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Program of Requirements Healthy Dwellings
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Marcel G.L.C. Loomans | Lada Hensen-Centnerová | Tim Beuker | Piet Jacobs |
Department of the Built Environment, Eindhoven University of Technology, Eindhoven, The Netherlandsm.g.l.c.loomans@tue.nl | Department of the Built Environment, Eindhoven University of Technology, Eindhoven, The Netherlands | bba binnenmilieu, The Hague, The Netherlands | TNO, Delft, The Netherlands |
Programs of Requirements (PoRs) help clients express what they want for a new or renovated building. In the Netherlands, PoRs have been developed for offices and schools with a focus on healthy indoor environments. They are well accepted and applied in Dutch practice. The PoR for healthy dwellings is an addition to support the creation of healthy dwellings. This article provides information about the considerations and details of this PoR.
Keywords: Indoor Environmental quality, health, comfort, practice, user influence, performance requirements, verification.
Introduction
In the Netherlands, Programs of Requirements (PoRs) have been developed for offices and schools [latest versions: PoR 'Healthy Offices' (Binnenklimaattechniek, 2023) and PoR 'Fresh Schools' RVO, 2021)]. The requirements in these PoRs focus on indoor environmental quality (IEQ) and aim to achieve healthy working and learning environments. All four main physical aspects of IEQ are addressed: indoor air quality, thermal, visual and acoustic comfort. The indoor environment addresses more aspects (see e.g. Loomans et al., 2011), but the focus is mainly on the physical parameters. The PoRs distinguish between classes. The lowest class, class C, corresponds approximately to the requirements of the Dutch Building Decree (as far as requirements have been set in this decree). Class B are requirements that assume a better IEQ, and class A is meant for occupants with more needs in terms of IEQ, e.g. due to health issues.
The PoRs for offices and schools have been available for almost more than a decade and are currently well used in Dutch practice for setting indoor environmental quality requirements. This is based on the number of downloads of these PoRs and the feedback from practice. It is an easy way for clients to communicate their wishes regarding IEQ. Validation of the requirements in the actual building is part of the process.
Given the success described above, and the fact that people spend a large part of their lives in their dwellings, a new initiative was started to develop a PoR related to IEQ in dwellings. This PoR was coined: "Healthy Dwellings".
This article provides information on the key assumptions used to develop the PoR Healthy Dwellings. Some examples of the PoR are given. The complete PoR is available free of charge (in Dutch; Binnenklimaattechniek, 2022). Note that this is also the case for the Healthy Offices and Fresh Schools PoRs.
Development considerations
The development of the PoR Healthy Dwellings was based on a combination of literature, guidelines and standards, knowledge from the PoRs for offices and schools, and feedback from two rounds of consultation with a focus group.
A number of assumptions were made in developing the PoR Healthy Dwellings. These assumptions formed the basis for how the PoR was ultimately presented:
· We assumed a close match with the IEQ indicators covering the four physical aspects of IEQ included in the PoR Healthy Offices and Fresh Schools. We have reviewed the literature to discuss the potential of adding other, dwelling specific, indicators and the health risk they may cause.
· All requirements have been formulated as performance-based as possible. This was done to avoid that new (innovative) solutions could not be considered. In fact, we hope that the PoR will stimulate innovation. In some cases, e.g. for Class A, the requirements have been formulated in such a way that we implicitly do not allow the use of certain known solutions.
· Similar to the other PoRs, we assume three classes, A, B and C. Class C largely corresponds to the quality level currently required by the Dutch Building Decree for new dwellings (Bouwbesluit, 2012). Class B requirements aim for a higher level of health and comfort. Class A provides a further improvement compared to class B. It is specifically aimed at a more sensitive target group, such as residents with respiratory diseases or a weakened immune system. A specific class can be targeted for each indicator. This should be decided by the customer. We have not yet ranked the indicators by health risk. This may be implemented in future versions.
· A dwelling contains different rooms (spaces) with clearly defined functions; e.g. bedroom compared to living room. In the PoR, we have differentiated the requirements for individual rooms for some indicators. Considering the fact that nowadays people work more often from their homes and bedrooms became offices during the day, we assumed a combined function bedroom and study room. Again, these requirements (class) can be set differently for each room.
· This version of the PoR focuses mainly on physical indicators, e.g. temperature, concentrations. When considering health, mental and social health could be considered in addition to physiological health. With a few exceptions, we have not yet explicitly included such IEQ indicators. An example in the current version is the indicator 'view to the outside'. Implicitly, of course, physical parameters can also affect mental and social health.
· An important final assumption is that we wanted to refrain from requirements that depend on user behavior, furnishings and use of the dwellings. This means that in the requirements we aimed at conditions that would result in a more robust dwelling when aiming for a higher class. This is reflected in the provision of a larger range within which the home should be able to be controlled. This is particularly visible in the thermal indicators. This is in contrast to the other PoRs mentioned. For air quality requirements, for example, we assume stricter values for a higher class with the perspective of additional contamination due to user behavior. We call this approach "action freedom".
Two examples of the requirements
Some (translated) examples for the PoR Healthy Dwellings are shown in Figure 1 and Figure 2. They show some requirements for air quality and thermal comfort. Note that this is only a selection of the indicators for which requirements are set. The full list includes 28 indicators, some of which relate to more than one performance requirement. Often the indicator requirements are accompanied by a short explanation (explanatory notes) to clarify what is meant.
AIR QUALITY | Class C - SUFFICIENT |
| Class B – GOOD extra as compared to class C | Class A -VERY GOOD extra as compared to class B |
CO₂ concentration & Air change rate | · The CO₂-concentration in residence rooms remains during use at maximum + 750 ppm above the outdoor concentration. |
| · The CO₂-concentration in residence rooms remains during use at maximum + 450 ppm above the outdoor concentration. | · The CO₂-concentration in residence rooms remains during use at maximum + 300 ppm above the outdoor concentration. |
· Assuming a normal, average metabolism (1.2 to 1.4 met) and a CO₂ production of maximum 0.005 ℓ/s per person it can be assumed that the Class C requirement is fulfilled if 25 m³/h per person fresh outdoor air is supplied. |
| · Assuming a normal, average metabolism (1.2 to 1.4 met) and a CO₂ production of maximum 0.005 ℓ/s per person it can be assumed that the Class B requirement is fulfilled if 40 m³/h per person fresh outdoor air is supplied. | · Assuming a normal, average metabolism (1.2 to 1.4 met) and a CO₂ production of maximum 0.005 ℓ/s per person it can be assumed that the Class A requirement is fulfilled if 60 m³/h per person fresh outdoor air is supplied. | |
· For the different rooms, the following numbers of people should be taken into account: - master bedroom: 2; - bedroom: 1; - living room: number of bedrooms + 1, with a minimum of 4 people |
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| · Residence rooms are equipped with a CO₂ monitor from which the instantaneous CO₂ value can be read. | |
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| · In order to relieve the residents, the ventilation for each room should be able to be controlled automatically based on CO₂ measurement. | |
| Explanatory notes: |
| Explanatory notes: | Explanatory notes: |
| · The Class C requirement for fresh air supply corresponds to the statutory minimum requirement as stipulated in the 2012 Building Code (new construction requirement: minimum 7 ℓ/s/room = 25 m³/h/room). |
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· The amount of air flow must be determined in accordance with the provisions of the NEN 1087 standard. Always use a zero-pressure compensated air flow meter for flow measurements. |
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· Although CO₂ sensors per room are not mandatory until Class A, application is recommended even as early as Class B and C because they provide great insight and can lead to awareness. |
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· If the local, instantaneous CO₂ concentration is unknown: assume an outdoor concentration of 450 ppm. Here it is taken into account that especially in inner city environments the CO₂ concentration is often elevated. |
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· It is assumed that the air in the occupied rooms is supplied and exhausted in such a way that a good flushing of the room is guaranteed; the ventilation efficiency (ratio between the quantity of ventilation air reaching the breathing zone and the total quantity of air introduced) is preferably at least 0.8 (see e.g. ASHRAE 62.1 for the ventilation efficiency of various ventilation concepts). |
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Humidity Living room, Kitchen, Bed room, Transfer room, Bathroom | · No requirements for the residence areas · Effective (automatic) control is provided that brings the humidity below 70% RH within two hours of using the bathroom. |
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Fungi Living room, Kitchen, Bed room, Transfer room | · There should be no visible mould on the walls or ceilings in the residence areas. |
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Volatile Organic Compounds | · The formaldehyde (HCOH) concentration is a maximum of 60 micrograms/m³. |
| · The formaldehyde (HCOH) concentration is a maximum of 30 micrograms/m³. | « |
· The total volatile organic compounds, or TVOC, concentration is a maximum of 200 micrograms/m³. |
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CO & NO₂ | · The carbon monoxide (CO) concentration does not exceed 10 milligrams/m³. |
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· If a central heating boiler is present, a CO detector should be present in that room. If one does not normally enter that room, the advice is to place the CO detector so that the alarm can be better heard. |
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· The nitrogen dioxide (NO₂) concentration does not exceed 40 ug/m³ on an annual average. |
| · The nitrogen dioxide (NO₂) concentration does not exceed 20 ug/m³ on an annual average. | · The nitrogen dioxide (NO₂) concentration does not exceed 10 ug/m³ on an annual average. | |
Particulate Matter | · The annual average PM2.5 (particulate matter) concentration is a maximum of 10 micrograms/m³. |
| · The annual average PM2.5 (particulate matter) concentration is a maximum of 7.5 micrograms/m³. | · The annual average PM2.5 (particulate matter) concentration is a maximum of 5 micrograms/m³. |
· Additional requirement regarding the particulate matter penetration through the façade and ventilation system (filter section): the PM2.5 (fine dust) concentration inside is maximum the outside concentration (hourly average indoor/outdoor ratio = 1). |
| · Additional requirement regarding the particulate matter penetration through the façade and ventilation system (filter section): the PM2.5 (fine dust) concentration inside is maximum the outside concentration (hourly average indoor/outdoor ratio = 0.5) | · Additional requirement regarding the particulate matter penetration through the façade and ventilation system (filter section): the PM2.5 (fine dust) concentration inside is maximum the outside concentration (hourly average indoor/outdoor ratio = 0.25) | |
| Explanatory notes: |
| Explanatory notes: | Explanatory notes: |
| · The mentioned upper limit for particulate matter concentration applies with normally switched on facilities (e.g., ventilation and heating). |
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· The premise is to avoid open flames indoors: no smoking, moderate use of candles and no fireplace, and to use cooking extractor with exhaust to the outside when cooking. |
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Figure 1. Description of the requirements for the CO₂ concentration and a selection of other IAQ indicators as part of the Air Quality requirements.
CLIMATE | Class C - SUFFICIENT |
| Class B – GOOD extra as compared to class C | Class A -VERY GOOD extra as compared to class B |
Comfort Winter Living room, Kitchen |
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· The operative temperature can be set manually between 16–23 °C. |
| · The operative temperature can be set manually between 16–24 °C. | · The operative temperature can be set manually between 16–24 °C. | |
· The desired end temperature can be controlled within a bandwidth of ± 1 K. |
| · The desired end temperature can be controlled within a bandwidth of ± 0.5 K. | « | |
· The above requirement regarding manual re-adjustment of temperature can be influenced with sufficient “speed”: temperature effect at least 1 °C per hour after adjustment. |
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| · In all residence areas, the temperature is measured and visibly fed back to the users. | « | |
Bedroom/Study room | · The operative temperature can be set manually between 16–22 °C. |
| · The operative temperature can be set manually between 16–22 °C. | · The operative temperature can be set manually between 16–24 °C. |
| · The desired end temperature can be controlled within a bandwidth of ± 1 K. |
| · The desired end temperature can be controlled within a bandwidth of ± 0.5 K. | « |
| · The above requirement regarding manual re-adjustment of temperature can be influenced with sufficient “speed”: temperature effect at least 2 °C per hour after adjustment. |
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| · In all residence areas, the temperature is measured and visibly fed back to the users. | « |
Bathroom | · The operative temperature can be set manually between 16–24 °C. |
| · The operative temperature can be set manually between 16–26 °C. | · The operative temperature can be set manually between 16–28 °C. |
| · The desired end temperature can be controlled within a bandwidth of ± 1 K. |
| · The desired end temperature can be controlled within a bandwidth of ± 0.5 K. | « |
| · The above requirement regarding manual re-adjustment of temperature can be influenced with sufficient “speed”: temperature effect at least 2 °C per hour after adjustment. |
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| · In all residence areas, the temperature is measured and visibly fed back to the users. | « |
| Explanatory notes: |
| Explanatory notes: | Explanatory notes: |
| · The winter comfort requirements are based on allowing occupants to raise the temperature in winter to the desired temperature. The system should be designed to achieve the above requirements. This allows the user to choose his/her own setting within the range at all times. |
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· The operative temperature refers (approximately) to the average of the air temperature and the average radiation temperature. In practice, the air temperature can be used unless a solution is chosen that specifically includes radiation. |
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· The operative temperature is determined in accordance with the provisions in NEN-EN-ISO 7726 and NEN-EN-ISO 7730. |
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· The above indoor temperature requirements apply unless the daily average outdoor temperature is lower than −5 °C. ‚Daily average outdoor temperature‘ here means (daily maximum + daily minimum) / 2. |
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| · These requirements assume a separate temperature control of the rooms | « | |
| · For lowering the temperature in winter, it may be assumed that residents use windows that can be opened. |
| · The above temperatures can be achieved regardless of the type of room and whether the temperature is adjusted up or down. For temperature reduction, the possibility of opening a window is not assumed. | « |
Figure 2. Description of the requirements for the temperature during winter as an example of one of the thermal climate requirements.
Verification
Defining requirements is part of the Program of Requirements and focuses on design. Whether the requirements are met in practice is an essential part of the PoR. A general requirement is that the requirements should be met for 95% of the occupancy time of the specific room. The occupancy time is defined for individual rooms.
The PoR Healthy Dwellings assumes three levels of verification to determine whether a dwelling meets the specified requirements:
1. Low level verification at handover. In order to limit the cost of verification, it is recommended that only the most important performance requirements are measured at handover, or that it is verified that the dwelling has been built in accordance with the design with respect to the aspects addressed in the PoR. Inexpensive measuring equipment such as temperature loggers and Class II noise meters can be used for these measurements. It is not possible (nor necessary) to verify all performance requirements. Some requirements require more extensive measurements.
2. Long-term monitoring with sensors. Because short-term measurements are less useful for some indicators, such as temperature, a relatively simple sensor network is required to monitor and verify the long-term performance of the home. This sensor network can be an integral part of the home, or it can be installed temporarily. Currently, not only temperature, but also CO₂ and PM2.5 concentrations can be measured with reasonable accuracy using low-cost sensors. Therefore, these indicators could also be included in long-term monitoring.
3. Detailed measurements in response to complaints. Some of the indicators require relatively complex measurements. It is recommended that the performance requirements for these indicators be verified only at the time of complaints. An example of such an indicator is draft.
Concluding considerations
The developed PoR Healthy Dwellings aims to support the development of dwellings that have health as a starting point and aim for (much) better indoor conditions than would be required based on the Dutch Building Decree. Ultimately, we hope that this will improve the health of the occupants and serve the public good. The PoR is closely aligned with existing PoRs for offices and schools. These PoRs are accepted and well known in the Netherlands. They are applied regularly. This means that it has become an accepted means of setting indoor environmental quality requirements for such buildings. Given this status and the desired alignment, we hope that the PoR Healthy Dwellings will be more readily adopted than other guidelines and schemes that are available, such as TAIL (Wargocki et al. 2021), BREEAM (BREEAM, n.d.) and Well Building (Int. Well Building Institute, n.d.). Although individual dwelling owners may use the PoR Healthy Dwellings to set IEQ requirements, we aim for housing corporations to be the early adopters who want to build or renovate a group of dwellings (new or refurbished) with a particular (health) class based on the PoR. Ultimately, we hope that higher class IEQ will also be recognized in the selling price or mortgage rates. We expect that this will support the application, as it can be directly translated into financial incentives to strive for a healthy living environment, similar to energy (NVM, 2022).
We see that the development of the PoR is not yet complete, but is still evolving. While there is room to extend the PoR to indicators that would serve a broader definition of health, i.e. mental health, or a need to rank the individual indicators in terms of health impact, we see an urgent need to develop the verification part. This process will begin with an assessment of existing dwellings to understand what procedure might work best and whether we can assess existing dwellings according to the defined classes. Once a complete, feasible and working verification procedure is in place, we plan to review the requirements on a regular basis to bring them in line with the latest available knowledge on IEQ requirements.
Acknowledgements
The development of the PoR Healthy Dwellings was initiated and financially supported by Binnenklimaat Nederland. We thank all members of the focus group for their active participation and input.
This article is a summary of the paper 'Program of Requirements Healthy Dwellings' presented at Healthy Buildings Europe 2023 in Aachen (Loomans et al. 2023). Part of the text of this paper was used to prepare this article. DeepL Write was used to improve sentences where deemed necessary.
References
Binnenklimaattechniek (2022) PvE Gezonde Woningen. Binnenklimaattechniek, Woerden. The Netherlands (https://www.binnenklimaattechniek.nl/document/publicatie-programma-van-eisen-gezonde-woningen-2022/ (accessed September 2023).
Binnenklimaattechniek (2022) Programma van Eisen Gezonde Kantoren 2021. Binnenklimaattechniek, Woerden. The Netherlands (https://www.binnenklimaattechniek.nl/document/pve-gezonde-kantoren-2021/ (accessed September 2023).
BREEAM (n.d.) BREEAM-NL richtlijn, https://richtlijn.breeam.nl / (accessed September 2023).
International WELL Building Institute (n.d.) WELL Certified | International WELL Building Institute | IWBI. https://www.wellcertified.com/ (accessed September 2023).
Loomans, M., et al. (2011) Key Performance Indicators for the Indoor Environment, in: P. Huovila (Ed.), World Sustain. Build. Conf. SB11, Helsinki, Finland.
Loomans, M. G. L. C., Hensen Centnerová, L., Beuker, T., & Jacobs, P. (2023). Program of Requirements Healthy Dwellings. In Healthy Buildings Europe 2023. Aachen. Germany. (https://research.tue.nl/files/301657527/Loomans_1215_A.pdf).
NVM (2022) https://www.nvm.nl/nieuws/2022/duurzame-woningen-presteren-beter/ (accessed December 19th 2022),
RVO (2021) Programma van Eisen Frisse Scholen 2021, Zwolle, The Netherlands, 2021. Rijksdienst voor Ondernemend Nederlands. https://www.rvo.nl/sites/default/files/2021/06/PvE-Frisse-Scholen-2021.pdf(accessed September 2023).
Wargocki, P. et al. (2021) TAIL, a new scheme for rating indoor environmental quality in offices and hotels undergoing deep energy renovation (EU ALDREN project). Energy and Buildings (Vol. 244), https://doi.org/10.1016/j.enbuild.2021.111029.
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