5. Examples of LowEx buildings

5.1 Summary table of case studies

5.2 Case studies

5.3 Retrofits

5.4 Advantages and limitations of LowEx systems

5.1 Example of an integrated design process

5. Examples of LowEx buildings

In this chapter, examples of the use of LowEx systems in various buildings are presented. Together with the findings from a literature study and an occupant survey, which are also presented in this chapter, the case examples give strong evidence that in addition to the desired heating or cooling effect, LowEx systems can provide occupants with a comfortable, clean and healthy environment.

The case examples show the wide variety of applications of LowEx systems. They also demonstrate the flexibility of the systems with regard to the energy source. There are examples of LowEx systems in dwellings and offices, but also in a museum, a church and a concert hall. In these examples there are systems that use heating or cooling energy from the sun, the ground, a district heating network as well as an electricity or gas network.

Findings from the literature (chapter 5.4.1) show that the application of LowEx systems provides many additional benefits besides energy supply, such as improved thermal comfort, improved indoor air quality and reduced energy consumption.

The Dutch occupant survey (chapter 5.4.2) shows that all low temperature systems are well received. In particular, the occupants found the indoor climate to be significantly better in dwellings with floor and wall heating compared to their previous dwellings. The main disadvantage was controllability. The advantages and disadvantages, mentioned by the occupants in the survey, are similar to results in the literature.

5.1 Summary table of case studies

Demonstration projects have been submitted by all participants: 27 examples plus 3 extra cases from the LowExx group. With 30 cases, distributed over new and existing buildings, residential and non-residential buildings with various technologies and emission systems, this gives a good overview of the application of LowEx systems for heating and cooling of buildings. Table 6 and Table 7 show the distribution of the cases. Most cases are new non-residential buildings. Floor heating is the most commonly used emission system in the case buildings. Most of the cases are low temperature heating cases; in only 12 cases high temperature cooling is applied. From the table on the following page you can get an overview of the cases. In chapter 5.2 the cases are presented in more detail.

Table 6. Distribution of building types

Table 7. Distribution of emission systems

Table 8.
Summary table of case studies

5.2 Case studies

In this chapter, 30 case examples of LowEx buildings from 11 countries are presented. The experiences from the case examples also agree with the findings from the literature: In addition to the desired heating or cooling effect, LowEx systems can provide occupants with a comfortable, clean and healthy environment.

The case examples are presented in fact sheets, 2 to 4 pages each. The first page of each fact sheet gives an overview on the project by a general description accompanied with a picture or drawing of the building. The heating and cooling system of the building is characterised with a list of keywords that are picked up from a selection. Some general data about the project team and the building is given. The installations are described with more detail in the following pages by words and schemes. Measurement results are presented where appropriate.

Cases are presented by country in alphabetical order. On the first page of each fact sheet, there is a map showing the locations of different case buildings in that country. The cases are numbered by country initials and number, (e.g. CAN 1, FIN 1, FIN 2, SWE 1, NLD 4).

Case examples

Figure 41. LowEx case buildings include many types of buildings, both new and retrofitted.

5.3 Retrofits

The existing building stock is very important to focus on, the renewal of the building stock is very slow, and if we neglect the possibilities for LowEx systems in the existing buildings, the total effect will not be as large as we hope for.

There are special issues to concern when we are talking about applying LowEx systems in existing buildings, these will be reviewed on the following pages. Some examples of LowEx systems in existing buildings are presented in the case examples (11 retrofit cases), one example is a historical building with a cultural heritage, which means an even greater challenge.

The age of the building is not such an important issue when considering the possibilities for applying LowEx systems. The important aspects are the degree of protection of the building, the building type, the scale of renovation, replacement of installation and the type of LowEx system to be applied.

A good timing is very important when trying to market LowEx systems into retrofits. When a renovation is done anyway, it is much easier and cheaper to install a new heating/cooling system than if you start a whole renovation just to change the system. In residential houses, it is very common that when the house owner changes, some renovation is done. Therefore, some marketing of LowEx systems should be made at the time of the purchase of the house.

Even though the low temperature heating systems are functional systems with lots of advantages, we need to keep in mind that when we are talking about retrofits, there are also some technical limitations. In old houses the walls are not always that good, and one can encounter really poor U-values. If this is the case, floor heating is not efficient enough to meet the heating demand. The exergy analysis tools developed in the Annex37 group can help with this problem. They calculate if the system is efficient enough to heat the house. Another problem could be that we can not make the floor any higher than it is. For this problem, there are solutions with very thin constructions, only a bit more than 2 cm for the whole construction (chapter 4, data sheet S.1.2).

5.4 Advantages and limitations of LowEx systems

5.4.1 Impact on IAQ, thermal comfort and energy consumption

The literature study presented here was conducted by (Eijdems et al. 2000) as a part of a Dutch program for the implementation of Low Temperature Heating (LTH) systems in buildings, which was initiated by the Netherlands Agency for Energy and the Environment (NOVEM). The primary goal of the program was to enable the use of Low Valued Energy as a heating source. Major savings in energy consumption can be realised by fully utilising the potential of Low Valued Energy.

The study by (Eijdems and Boerstra 1999) shows that lowering the temperatures for heat distribution systems, besides the possibilities of savings in energy supply, gives additional benefits in the fields of:

• Indoor Air Quality (particles, mites, lower air temperature, annoyance and dust);
• Thermal Comfort (radiant heat, temperature gradient, radiant heat asymmetry, floor temperature, temperature fluctuations, heating up period, cooling, air velocities and draught);
• Energy Consumption (transmission/venting losses, transport energy, utilisation of gains).

By highlighting these additional benefits, an easier introduction of LTH systems might occur. Application on a broader scale will also lower the prices of these systems.

As explained in chapter 1, to realise global objectives of energy saving and emission reductions in the built environment, the use of ‘Low Valued Energy’ is necessary. Low Valued Energy is available from residual heat, ambient heat and renewable sources. It can be used for Low Temperature Heating (LTH) in residential and commercial buildings. For this purpose the buildings and installations should be designed for low temperature distribution systems. Appropriate distribution systems, like floor and wall heating, have a life cycle of 40 to 50 years. So to implement Low Valued Energy sources within the next half of a century, heat distribution systems should be designed for lower temperatures as soon as possible. Aware of this need, the NOVEM initiated an implementation program in 1996, which included studies (feasibility and theoretical), field experiments, demonstration projects, etc.

The heating of buildings is often accomplished by a heat distribution system operating at high temperatures (90-70 °C). In the Netherlands the most common heating systems (especially in residential buildings) are built up from the following components:

• gas boiler with improved or high efficiency;
• piping system based on hot water as a heat transport medium and
• radiators or convectors as heat supply elements.

To realise an indoor air temperature of about 20 °C, the system water is heated up to a maximum of 90 °C, by a gas flame in the boiler of approximately 1200 °C!

The actual design methods for heating systems are based on the utilisation of this huge temperature drop. From sustainable heat sources (like solar, geothermal and waste heat) a much smaller temperature interval is available. Heating systems can only utilise these sustainable sources when they are able to operate properly at significantly lower temperatures. Wall and floor heating systems fit especially well into a LTH design. But also air heating, enlarged radiators and enlarged convectors can be applied.

Due to a better insulation level of new and retrofitted buildings and new techniques for reducing ventilation losses, the heating demand of modern buildings is decreasing. This ongoing trend enables a broader application of LTH systems for the smaller heating capacities needed. To define LTH systems, a distinction between design temperature ranges is given in Table 9.

Other benefits can be obtained by using LTH systems. In general, a better thermal comfort and better indoor air quality is reached due to lower temperatures and larger surfaces. Furthermore, additional energy saving occurs through a better efficiency of boilers, less pipe heat losses and lower venting losses. In a Dutch study, the qualitative aspects of LTH systems have been researched, mainly based on literature review. This study has been reported in (Eijdems & Boerstra 1999).

Table 9. Definition of temperature ranges for heating systems (from Dijk et al. 1998)

1 Cauberg Huygen Consulting Engineers, Amsterdam, The Netherlands
2 BBA Indoor Environmental Consultancy, Rotterdam, The Netherlands

5.4.1.1 Thermal comfort

Radiant heat transmission

The radiant heat transmission components of LT systems are much higher than in other systems. Due to large surfaces and low temperatures, the radiant component of floor and wall heating is about 50–70 %. For conventional HT radiators this is 20–40 % (Zöllner et al. 1985). Therefore, the heat transfer by air is reduced and the air temperatures can be 1–2 °C lower at the same comfort level. Experimental studies show a high appreciation by the building occupants for heating systems that work primarily on radiant heat (Dongen 1985). It is presumed that radiant heat transfer (i.e. relatively cold air and warm surrounding surfaces) suits better to thecomfort needs of human beings because it is more ‘natural’ (like solar radiation on the skin).

Vertical temperature gradient

In computer simulations and laboratory and field experiments, a clear difference of vertical temperature gradients was found between floor and HT radiator heating. With floor heating, practically no gradient is found in well-insulated buildings (Dijk et al. 1998, Olesen 1997, Cox et al. 1993). Radiator, wall and other heating systems are much more dependent on a good design. Normally gradients range from 2-3 °C between the floor and ceiling. Poorly designed systems show gradients up to 7 °C. In particular, the gradient between the ankle and head level has influence on the perceived thermal comfort.

Temperature asymmetry

Cold window surfaces can cause discomfort by radiant heat losses which are not in balance with radiant heat flows in other directions. Complaints occur when differences exceed 23 W/m² or 10 °C (Erhorn and Szerman 1988). Conventionally, compensation was provided by placing hot radiators close to the cold surfaces. Due to better glass types with a high insulation grade, this aspect is loosing importance. At U-values of the glazing under 1.5 W/m²K no significant differences between heating systems occur (Olesen et al. 1980). At higher U-values the height of the window can be restricted or compensation, for instance by extra heating in the outer circle of the floor heating system, is recommended. Discomfort from heated floor or wall surfaces does not occur.

Surface temperature of heated floors

A heated floor raises the comfort for all kinds of users. Floor covering, like carpets, is not needed for walking barefoot or sitting on the floor (at home, in nurseries, by swimming pools, etc). Optimal floor temperatures range from 20-28 °C with shoes and 23-30 °C barefooted, depending on the flooring material (maximum 28 °C recommended for all purposes; (Olesen 1997)). Outside the living zones (e.g. within 0.60 m from the walls) up to 33 °C is allowed. A study for increased bacteria growth on feet with heated floors showed no significant result (Theuss et al. 1994).

Temperature fluctuations

Quick temperature fluctuations around a constant mean value cause discomfort. LTH systems have a greater inertia than HT radiators or air heating. Moreover, the driving forces are smaller due to large surfaces and low temperature differences. For these reasons fewer fluctuations occur. The inertia is often considered to cause discomfort at incoming solar radiation or sudden changes in internal gains. In this aspect, LTH systems profit from their ‘self-regulating’ abilities. Due to the small temperature ranges at which they operate, the heat supply reacts instantly on indoor temperature changes (Olesen 1997 and 1998), (Fort 1995).

Heating up period

Conventional heating systems have a shorter heating up period (after cooling down e.g. for 8 hours) due to the inertia of the directly connected thermal mass of floor and wall heating systems. An important factor is the connection between the tubes and surrounding material and the mass of the material. The temperature raise for LTH systems, however, is much lower than for HT systems. Moreover, heating up is often associated with air temperatures. When the operative temperature (mean value of air and radiant temperature) is observed, the differences between LT and HT heating systems reduce. For (very) well-insulated buildings the energy gain from a night set back is small due to limited cooling down of the thermal mass within the insulation envelope. Therefore, a minor set back is recommended in combination with LTH systems (Eijdems and Boerstra 1999), (ISSO 1985).

Cooling abilities

Increasing the insulation grade of buildings together with the reduction of ventilation losses and utilisation of solar gains causes the risk of overheating during summer time (Poel and Eijdems 1991). LTH systems often give easy opportunities for cooling. Especially when combined with a ground collector (and heat pumps), a limited capacity of (high temperature) cooling can be accomplished by minimal effort (Olesen 1997). A ground collector can be regenerated from the cooling load. Other costly devices to compensate overheating can be avoided.

Air velocities and draught

Draught can be caused by cold (window) surfaces, at which the air in the boundary layer cools down and flows downwards. This might be avoided, for instance, by placing hot radiators under the window. Laboratory studies show that mean air velocities for HT radiators and floor heating are in the same order within the living zones. The fluctuations around the mean value however (turbulence-degree) are about 20 % higher with HT radiators (Olesen 1998, (Peng 1996). Applying well-insulated glazing and limited window heights (max. 1.7 m for clear double-glazing) reduces sufficiently the risk of draught with floor (and likely other LT) heating systems. Special attention is needed for natural supply grills in the facade for venting.

5.4.1.2 Indoor air quality

Suspended particles

In a field study in Finland, visible dust on floors was found to correlate to neurological complaints, like headache, fatigue, concentration problems etc. LT heating was found to give less eye-irritation and throat and other mucous membrane diseases (Sammaljärvi 1998). Also, a correlation was found between the temperature of the heating surface and particle deposition. It is assumed that the lower grade of air fluctuations from LTH systems causes a lower quantity of suspended particles in buildings (Lengweiler et al. 1997).

House dust mites

Many studies show that floor heating has a positive effect on the reduction of the house dust mite population in dwellings e.g. (Schata et al. 1990). This is mainly caused by lower relative humidity (RH) in the boundary layers above the floor (within the floor covering). The house dust mite survival threshold is RH under 45 % in the long term. The influence of a floor heating system on the RH in the boundary layer is calculated to be in the order of 10 %. This reduction is just sufficient to bring the RH under the threshold value.

Room Air temperature

As a result of the high contribution of radiant heat, the room air temperature can be 1-2 °C lower for LTH systems. Several studies show a better performance for stuffiness and perceived air quality at lower air temperatures (e.g. Fang and Fanger 1997). Mucous membrane irritation complaints increase significantly at air temperatures over 22-24 °C (Skov and Valbjorn 1990). The annoyance from all kinds of emissions (TVOC etc) is correlated to air temperature. A correlation also was found for Sick Building Syndrome and air temperature.

Dust singe and odour annoyance

Inhaling dust can cause allergic reactions (Mølhave 1996). The sensitivity of humans for inhaled particles is more dependent on the quality of the particles than on the quantity (Fang and Fanger 1997). At temperatures exceeding 55 °C the process of dust singe starts. The particles get more reactive and irritating at the higher temperatures that occur in HT heating elements (Sammaljärvi 1998). So LTH systems not only give less suspending particles in the air but, moreover, the particles spread less aggressively due to the absence of dust singe.

Transmission losses

Due to floor and wall heating the mean temperatures in the heated constructions are higher during the heating season. Extra heat losses to the backside of the constructions will occur. For heated floors above a crawl space this is about 40 MJ/m² per year with Ufloor=0.36 W/m²K and in the average Dutch climate (5 % of the supported energy flow). Heated walls in the outer envelope show an increase of losses even up to 50 % (Dijk et al. 1998), (Olesen (1997 and 1998), (ISSO 1985). Applying a thicker insulation layer (plus 2.5-5.0 cm) in heated constructions can easily compensate for these extra losses. Transmission losses from hot air flowing along window surfaces are reduced with LTH.

Ventilation and infiltration losses

In buildings with LTH ventilation losses are lower due to lower air temperatures. Especially infiltration and natural venting cause less energy consumption. In a new Dutch standard dwelling the saving is about 1.6 GJ (5 % of the total consumption) per year (Dijk et al. 1998), (Olesen 1997 and 1998). For ventilation systems with balanced air exchange and heat recovery the saving is smaller.

Transport energy

Larger flows of the heating medium might need to be transported because of lower temperature intervals (especially with floor heating). In combination with a heat pump a continuous heat flow is preferred at the lowest supply temperatures possible. Therefore, the working time of the transport pump often will be longer for LTH systems. Extra transport energy can be restricted by a good hydraulic design to about 400 MJ electricity per year (on an average domestic electricity consumption of 10 GJ/year).

Utilisation of gains

In buildings with an average insulation level, solar and internal gains are utilised 100 % for reduction of auxiliary heat demand. In light mass buildings with an improved insulation the utilisation of gains decreases. In simulation and laboratory studies energy savings of 3 % were found for floor heating systems under these circumstances (Fort 1995). Theoretically the savings can reach up to about 5-12 %. The energy saving from better utilisation is also dependent on the layout of the heating system and thermal zoning in the building (e.g. through transport of solar gains by a floor system from south to north zones).

5.4.1.4 Summary of the literature review

Low Temperature Heating (LTH) systems mainly show qualitative advantages:

• Thermal Comfort increases in many respects (greater share of radiant heat transfer, less temperature gradients, better floor contact temperature, less draught and air turbulence);
• The IAQ is also positively influenced (less dust singe and house dust mites, less stuffiness and odours through lower air temperature, less suspended particles);
• In addition to the ability to use Low Valued Energy savings are gained from better performances of boilers and heat pumps, less piping heat loss and less ventilation losses.

Other benefits might occur, like avoidance of burning risk, extra space due to the absence of radiators, avoidance of mould growth, etc. Many disadvantages can be avoided by means of a proper design and compensating measures. Arguments against LTH systems often appear to be based on negative experiences in the past (bad design or insulation) or a lack of knowledge.

5.4.2 Occupants’ experiences on Low Temperature Heating systems

One of the critical success factors for the implementation of Low Temperature (LT) heating systems in residential buildings is the way these systems are viewed and accepted by the occupants. At the moment costs for such systems for dwellings are higher than those for traditional High Temperature (HT) systems while energy savings in some cases are only marginal. This means that LT systems must have some additional qualitative benefits for occupants (thermal comfort, indoor air quality, safety, etc.). The overall performance of LT heating systems must be at least equal or preferably better than that of traditional HT systems.

An occupant survey was conducted in the Netherlands in October 1999 among 409 households with LT heating systems Silvester et al (2000). The first objective was to make an inventory of the experiences of occupants with LT systems, and to see if these systems fulfil their expectations. These results can also convey information about possible obstacles in further market introduction.

Heating system in previous dwelling

The majority of the occupants did not have any previous experience with LT heating systems as most of the previous dwellings (77 % for floor heating to 94 % for wall heating) had central heating systems with HT radiators (the most common system in the Netherlands). Six percent of the households had floor heating in their previous home.

Selection of dwelling in relation to LT heating

Similar surveys (demonstration projects of sustainable buildings) show that occupants do not select homes because of environmental reasons alone. However, for 58 % of the households the environmental aspects of the home contributed to the final decision, which also corresponds with scores from other similar surveys. The score for households with LT radiators is particularly notable: for 65 % of the occupants, environmental aspects and measures were important in their decision when selecting a home. The presence of wall heating was an important aspect in the selection process for 35 % of the inhabitants. For floor heating this was as much as 71 %.

Also notable was that if environmental aspects were considered in relation to the presence of LT heating systems, floor heating systems were considered to give a positive contribution to the dwelling but were not considered as an environmental or energy saving measure.

Use of dwelling and heating system

Set point of heating

Occupants were asked about the set points of the thermostats for a winter evening and a winter night (Table 10). The objective of this question was to get an impression of the use of the different LT systems.

Table 10. Set point temperature.

For a winter evening the set point temperature for floor heating was significantly lower (0.7 °C) than that for radiators. For a winter night the difference in set points was significant both for radiators as well as for wall and floor heating.

Heating and ventilation of bedrooms

Up to 50 % of the households did not use heating in bedrooms at all during winter. In dwellings with floor heating, it seems that bedrooms were heated more (in case bedrooms were heated). No explanation could be found for this.

As in most Dutch houses, ventilation was used for long periods during wintertime. Notable is that in dwellings with wall heating, in 47 % of the cases ventilation was used for several hours. In one of the projects, where all dwellings were equipped with wall heating, 58 % of the households used ventilation for six hours a day. It is possible that the slowness or the poor(er) controllability of the system are reasons why occupants wish to control the temperature by opening windows. However, no such evidence was found in this survey. One project was equipped with floor heating on both floors. However, this project did not show any significant difference in ventilation compared to projects with LT radiators.

5.4.2.2 Appreciation of the indoor climate

Appreciation of the heat

Both the radiant temperature as well as the air temperature affect thermal comfort. However, it is difficult to translate the difference between air and radiant temperature into a level of appreciation. Occupants were asked to give their appreciation of the heat according to a scale reaching from "very pleasant" to "very unpleasant". Floor heating scored a little better than wall heating. Relatively, there were more occupants who judged LT radiators as "quite pleasant" or "unpleasant"(Figure 42).

Figure 42. Do you think that LT system gives pleasant or unpleasant heat?

Cold draught near windows

Wall and floor heating have a higher risk of discomfort caused by proximity to cold windows (cold draught). This risk was confirmed by the results of this survey. Households with LT radiators had fewer problems with cold draught during frost temperatures than households with floor and wall heating. Especially in households with wall heating, 41% of the cases had problems with cold draught near windows in the living room during frost temperatures.

Dust in the air

Occupants were asked to compare indoor air quality in their current dwelling with that in their previous dwelling in relation to dust in the air. Particularly notable is the response from occupants in dwellings with wall heating: 88 % indicate that indoor air quality in relation to dust had improved. For the other dwellings (floor heating and LT radiators) no significant change was noted.

Evaluation of the indoor climate

Occupants were asked about their opinion of the indoor climate in terms of whether or not it had improved in relation to the indoor climate in their previous dwelling. Notable, again, was the very positive score for floor and wall heating (>70 %). Up to 61 % of the occupants with LT radiators did not notice any difference. The results for wall heating do not differ from previous occupant surveys (demonstration projects for sustainable building – Silvester and de Vries) (Figure 43).

Figure 43. Do you think that LT system gives an improvement of the indoor climate or not?

5.4.2.3 Functioning of the heating system

Controllability of the heating systems

Floor and wall heating are often associated as systems with a slow reaction time. However, modern systems seem to react much faster. For this reason occupants were also asked about their experiences of the heating up time after a longer period of absence.

The majority of the occupants both with floor heating (55 %) and wall heating (65 %) indicated that the heating system does not heat up the dwelling very fast. Up to 68 % of the occupants with LT radiators reported a fast heating up time (Figure 44).

However, these scores did not seem to affect the occupants’ satisfaction with the controllability of the temperature. A minority of the occupants were dissatisfied with the controllability of their heating system. There was no significant difference between floor heating (10 %) and wall heating (12 %). The score for LT radiators was a little better (5 %) (Figure 45).

Figure 45. Satisfaction with the controllability of the temperature.

Failures of the heating systems

The occupants were asked about the overall functioning of their heating system. Many households (44 %) had problems with their heating system during the first months of habitation in their new home. The occupants could not repair these failures themselves. Notable is that the most common of the systems (LT radiators) had the highest percentage of failures (48 %). Wall heating had the lowest score with 23 %.

Quality of information

For 64 % of the respondents, the information about energy and environmental aspects of their home was sufficient. However, the information was perceived to be clearer for wall heating (79 %) and floor heating (73 %) than for LT radiators (40 %).

The combination of floor heating with heat pumps resulted in many unanswered questions by the occupants. These questions concerned for example the exact working of the system, the advantages and disadvantages of the system, and the costs for heating (structure of charges). Also more general information was desired about the innovations and the long-term maintenance as well as some guidelines about how to use the system as efficiently as possible.

5.4.2.4 Evaluation of LT-systems

Satisfaction with the different LT-systems

Occupants with LT-radiators were less satisfied with their system than those with the other two systems (Figure 46). Results concerning satisfaction with wall heating and floor heating do not show significant differences; 70 % of the occupants were satisfied with their system. The evaluation of the LT heating emission system and the total heating system (including heating source) were very much related.

Relation between evaluation of the heating with evaluation of DHW system and ventilation system

The assessment of different building services systems in a dwelling can be strongly affected by the malfunctioning of only one of the systems. Also, a very high appreciation of one of the parts can mask problems within other parts of the system. The relation between the heating system, DHW system and ventilation system was studied and analysed. This evaluation shows that the assessment of the DHW system is not related to the assessment of the heating or the ventilation system. The assessment of the ventilation system however correlates with the heating system in that occupants who are satisfied with the functioning of the heating system are also satisfied with their ventilation system and vice versa (Figure 46).

Figure 46. Satisfaction with LT heating system /heating in general.

Advantages and disadvantages

Occupants were asked to mention the advantages and disadvantages of their heating systems. The results are shown in the following tables (only scores of 5 % or higher).

Floor heating

As advantages of floor heating the occupants mentioned:

As disadvantages of floor heating the occupants mentioned:

The appreciation of the floor heating in one of the projects seemed to be more affected by problems connected to the heat source than by actual problems within the emission system. Occupants were also unsatisfied with the promises of utilities concerning the low energy consumption of heat pumps (during the first year).

Wall heating

In two projects a wall heating system was applied as the main heating system. In total, data from 17 dwellings is available. In 35 % of the households, wall heating was a major decisive factor when choosing a house.

As advantages of wall heating the occupants mentioned:

As disadvantages of wall heating the occupants mentioned:

LT-radiators

Most of the selected projects have LT radiators. In this survey, this group with 113 households is over represented.

As advantages of LT-radiators the occupants mentioned:

As disadvantages of LT-radiators the occupants mentioned:

5.4.2.5 Summary of the results of the occupants survey

Results of this survey can not be generalised for the total Dutch new building stock. All studied projects were demonstration projects for LT systems.

Occupants did not initially choose dwellings based on environmental factors. However, for 58 % the environmental aspect was important in the final selection of their dwelling. Floor heating is an important factor in the decision-making but is not considered as a particular energy or environmental measure. Therefore, additional information and communication concerning the energy efficiency of LT systems is recommended.

A majority of the respondents with LT-radiators did not have any idea that they have an LT-system. On one hand this is positive because this suggests that there seems to be no difference (disadvantage) in comparison with more conventional systems. However, further communication about the energy efficiency of these systems could still be recommended.

There was a significant difference between the set points of the thermostats between the different LT systems during winter nights. Occupants with floor and wall heating applied a small temperature difference to compensate for night set back. Occupants would also be interested in learning how to use their heating appliances to reach an optimal balance between energy use and thermal comfort. About 50 % of the occupants did not use heating in bedrooms during wintertime.

The advantages and disadvantages, mentioned by the occupants in this survey (Table 11) back up results from previous research. This survey also confirms the results of the literature review on side effects of LowEx emission systems (chapter 5.4.1). Especially the occupants´ perception of indoor air quality, thermal comfort, slowness and controllability of some LT-systems confirm results from previous studies.

Although LT-systems are very well accepted and appreciated, there are some negative aspects and disadvantages that should be taken into account and solved. These are for example system controllability per room (floor and wall heating) and the size, design and installation of LT radiators.

All systems were very well received by the occupants. Particularly indoor climate has improved a lot in dwellings with floor and wall heating in relation to their previous situations. For LT radiators the occupants found no difference in the indoor climate compared to their previous dwellings. The main disadvantage is the poor controllability, especially with floor and wall heating; 30 to 40 % of the occupants mention poor controllability as a disadvantage.

Table 11. The survey gives a good indication of the specific advantages and disadvantages of each system.

5.4.3 Experiences from case studies

User experiences

Several case studies include feedback from occupants about their experiences with LowEx heating or cooling systems in their buildings.

This information is available for the following cases:

• Netherlands: Amboise, Weerselostraat, Molengronden, Rijkswaterstaat
• Canada:Downey Road
• France:Hotel de Croy
• Japan:IDIC Research Centre, Kumamoto, Sustainable Eco-house, YIES
• Sweden:Villa Akander, Villa Wahlin
• Germany:ZUB Centre for sustainable Building

In general, the feedback from users has been very positive. In all cases the occupants were satisfied with the installed LowEx systems.

Residential buildings

In the existing dwelling Villa Akander, occupants felt that the thermal comfort had significantly increased after the installation of the floor heating system. The Kawasaki Sustainable Eco House provides a high level of comfort for the occupants in the heating as well as the cooling case (fresh and dry air). Children living in the neighbourhood like to visit this house because of its comfort level. Also the Dutch case studies show that the occupants were satisfied with the LowEx systems. Occupants of the Amboise project mentioned that the wall heating system played an important part in their decision to buy the house. The occupants also preferred a lower set-point of the thermostat compared to the one they were used to earlier (19°C in stead of 21°C).This confirms the assumption that wall heating is equally comfortable at lower air temperatures than radiator heating.

Non-residential buildings

Users of the ZUB-building indicated to be satisfied with the indoor climate in the building. In the cooling case of Hotel de Croy, occupants appreciated the reached comfort and they particularly praised the absence of noise and air movement. IDIC reported a highly satisfying indoor climate both for human occupants as well as for indoor plants. Also Kumamoto occupants stated that the building provides a healthy work environment under different seasonal climates, particularly during the hot and humid summer period. In the YIES building the majority of the occupants claimed to be satisfied, although there were some remarks about the relatively slow heating-up time of the floor heating system.

Finally, a survey among the users of the RWS office in Terneuzen showed significantly higher occupant satisfaction with indoor climate compared to standard offices. There were no complaints at all regarding dry air, air dust, and air quality in general; and significantly fewer complaints concerning eye irritation, temperature fluctuations and overheating.

Measurements

Measurements have been performed in most of the case studies in order to gain a better insight in system temperatures, air and radiant temperatures, heating up time and air temperature distribution (thermal gradient). Also energy (exergy) consumption has been evaluated. More details can be found in the paragraphs describing the case studies.

Conclusions

The user experiences from the case studies support the findings of the literature review on the "impact on IAQ, thermal comfort and energy consumption" of LowEx systems described in paragraph 5.4.1. The measurements performed in the case studies also coincide with the results of the literature review.

It can therefore be concluded that the experiences from the case studies (measurements as well as user experiences) confirm the conclusions of the literature review.

Interestingly enough, LowEx systems are not only preferable from an exergy point of view, people also seem to appreciate the "softer" heat and coolness of the LowEx systems much more than the traditional heating and cooling solutions.

Figure 47. The users of the RWS office (case NLD 5) in the Netherlands were significantly more satisfied with the indoor climate compared to standard offices.

5.5 Example of an integrated design process

In section 4.4 we have given guidelines for the design process of LowEx heating and cooling systems for buildings. However, there are many ways to end-up with choosing a LowEx heating or cooling system. This section describes the methodology used to design the 421 Downey Road demonstration building in Canada. It describes the objectives that the design team was given and how these were met through an integrated design process. The cost of the building was not increased, but the energy performance, thermal comfort and flexibility of the building were all improved as a result of the integrated design process, which led to the implementation of a LowEx heating and cooling system. A complete description of the process can be found on the CD-ROM version of the LowEx Guidebook (Guy et all. 2003).

There are many benefits to incorporating LowEx HVAC systems into buildings, yet the implementation has been sluggish despite the fact that there are many systems available. One of the main reasons for this may be that current design methodologies tend to result in traditional design solutions that require little innovation and have a low capital cost, rather than innovative solutions that reduce life cycle costs. The concept of exergy is very useful for understanding the efficiency of energy conversion from one form to another and the sustainability of buildings Shukuya and Hammache (2002) but building owners and designers base decisions on more measurable quantities like energy consumption, occupant comfort, and most often cost. Therefore, a design process that incorporates these important factors and is relatively straightforward to adopt is required to increase the implementation of LowEx systems. In this chapter, the integrated design process that was applied in the Canadian LowEx demonstration project is presented. It is interesting that the design process started with the important parameters from the owner’s point of view (cost, rentability, energy, comfort, productivity and sustainability) and resulted in a LowEx solution (radiant heating and cooling panels).

421 Downey Road

421 Downey Road is a 4.830 m² research laboratory and office building located at Innovation Place on the University of Saskatchewan campus in Saskatoon, Saskatchewan, Canada. The building and all buildings at Innovation Place are provided with heating and cooling from a local central heating and cooling plant. It is very important to note that the building owner (Innovation Place) rents out the buildings in the research park to research and development companies. Therefore, the owner builds, maintains and operates the buildings and thus is more interested in the function of buildings over the building life cycle compared to, for example, a developer who will sell the building after it is built. Nevertheless, a developer that successfully applies the principles presented in this paper should be able to obtain a higher price for the building, than a developer who simply reduces the first cost. More details on the 421 Downey Road building can be found in the fact sheet.

Design objectives

The main objectives of the building, which were provided by the building owner, are listed in Table 12. In order to achieve these goals of improved energy consumption, sustainability and flexibility at no extra capital cost, it was evident that numerous design decisions that are traditionally made in isolation must be integrated and balanced for an acceptable solution.

Table 12. Objectives of the 421 Downey Road building.

Integrated design process

The flow chart of the "Integrated Design Process" shown in Figure 48 outlines some of the key tasks required to achieve cost-effective, advanced designs within the time normally allocated to a project. In the beginning, it is important to set clear project goals and provide a default design that works for the climate and type of building under consideration so that the building can be completed on schedule. This default design, termed the "70 % solution", is an active document that is developed with input from project management, operations and maintenance, leasing, property management, security and lessons learned from previous projects. This document is presented at the first design meeting for three very important reasons: (i) it helps set the "milieu" for the project, indicating that this is not a traditional design; (ii) it provides a 70 % solution based upon proven designs, which helps to minimize concerns about liabilities and improves the efficiency of the design process; and (iii) it sets the framework for the interaction required for integrating architectural, mechanical, structural, electrical, lighting, controls, networks and other building systems. After the initial design meeting, each consultant should be motivated to be part of the integrated design process.

As shown in Figure 48, a key to the integrated design process is the integration of the mechanical, electrical, architectural and controls designs, which can be highlighted by the following example. If the architect designs an efficient building envelope and the electrical consultant design an energy efficient lighting system (both will reduce the building heating and cooling loads), then the mechanical consultant can adopt a lower capacity heating and cooling system (or even a LowEx heating and cooling system) and the control consultant can adopt a simpler controls system. In this case, the potential extra cost for the building envelope and lighting systems, can be recovered by the potential reduced cost of the HVAC and controls systems. In addition, energy and productivity savings will accrue over the life of the building. In this way, the decisions of each consultant are balanced during the design process.

Figure 48. Flowchart of the integrated design process.

Integrated design team

A critical step in the integrated design process is to establish a team that has the capabilities and motivation to meet project objectives. The key to the success of the project is to challenge traditional design and construction methods and motivate the design team to collaborate on the design and implementation of advanced building techniques. This usually means changing the structure so that members of the team are free to contribute to the design without barriers imposed by traditional structures and percentage of contract design fees (Figure 49). For the integrated design team to be successful, it is critical that the project manager have design integration skills. In many cases, the project manager will manage the project with assistance from a coordinating consultant. In Figure 49 the coordinating consultant is shown as the structural consultant, but any of the consultants could perform this task depending on their skills and experience. Consultants report directly to the project manager and the coordinating consultant manages the design development process.

At Innovation Place, the integrated design process has been successfully used to design several buildings including the 421 Downey Road research laboratory and office building. The integrated design process resulted in a rentable, attractive corporate space due to excellent comfort and indoor air quality. In addition, the energy consumption was reduced and the project was completed with no additional capital costs. The integrated design process focused the integrated design team on total building performance rather than sub-system performance. A key component of this was that the design consultants were compensated based on the time and effort spent on the project rather than on a percentage of the capital equipment they specified. This process led to the selection of an efficient heating and cooling system using radiant ceiling panels and a ventilation system with a high effectiveness heat recovery system. These LowEx systems helped improve building performance without an increase in capital costs. The owner and clients have been very satisfied with the results.

Figure 49. Comparison between the integrated design team and a traditional design team.