COMFORT AND INDOOR AIR QUALITY IN PASSIVE HOUSES IN THE U.S Mike Beamer Eugene, OR 9 Email: mike@obliquecontent.com Sophia Duluk Eugene, OR 9 Email: sophiad@gmail.com David Bisers Eugene, OR 9 Email: davebisers@gmail.com Diana Hogard Eugene, OR 9 Email: diana.hogard@gmail.com Alison Kwok Eugene, OR 9 Email: akwok@uoregon.edu ABSTRACT With the growing popularity of Passive Houses within the U.S., post-occupancy evaluations of the standard are essential in validating the Passive House performance to the public. The post-occupancy evaluation performed and proposed by this study focuses on thermal comfort, indoor air quality and energy use. Relatively new to North America, this German-based standard specifies energy targets, envelope enhancements, and several environmental principles to provide thermally comfortable buildings and healthy indoor air quality. This study seeks to verify the success of this construction type through participation of a select number of building owners. A question survey was developed and sent to the building owners in addition to a toolkit of equipment and a set of instructions detailing the data collection process. Data collected included: indoor and outdoor temperatures, carbon dioxide levels, humidity, window-wall surface temperatures, and comfort attitudes, behaviors and perceptions. The study has shown that the houses were performing well; occupants were thermally comfortable, carbon dioxide readings were, in most instances, below recommended levels, and the window-wall (window and surrounding wall surface) temperatures stayed within F or F of ambient temperatures. building, creates thermally comfortable buildings, and provides healthy air quality. An airtight envelope and super insulation reduces air infiltration and provides consistent and comfortable indoor temperatures and significantly reduces heating and cooling energy. The Passive House standard was developed in Germany in the early 99 s; since then there have been more than, houses, schools, and commercial buildings built to the Passive House standard in Europe. In the U.S. twenty-five buildings have received Passive House certification since. This study will examine the standard s performance through researching thermal comfort, indoor air quality and energy use by studying Passive Houses within the U.S.. INTRODUCTION The Passive House standard provides performance targets for buildings to reduce energy use by 9% from the average Fig. : Passive House conceptual cross-section (from Wikimedia Commons)
In many cases, the heating demand in Passive Houses is so small that it can be met by utilizing internal gains (heat from occupants, appliances, and lighting) and solar gains. The Passive House standard claims to provide up to a 9% space conditioning energy reduction over typical buildings. The theory behind thermal comfort in Passive Houses is to maintain uniform comfortable temperatures near windows humans are acutely aware of the coolth near single-paned windows on a cold winter day, where the body feels cold as it loses heat to the window. The Passive House standard influences comfort by requiring window-wall temperatures to be within F of the interior set-point temperature which is usually F. Another requirement in the Passive House standard is airtight construction. Air infiltration is typically tested twice during the construction phase; once before the insulation is installed to confirm success of the taping of the air barrier; and once after the walls are closed in. In order to maintain good indoor air quality, every Passive House must be equipped with a heat recovery ventilator (HRV, or energy recovery ventilator, ERV); a device that constantly ventilates living spaces while recovering heating and cooling energy produced inside the envelope. This mechanical system operates continuously to provide fresh outdoor air. For the purposes of this study, carbon dioxide levels will be used as a predictor of general air quality which includes odors and bioeffluents; not as an indicator for health hazards. This paper focuses on thermal comfort and air quality in a selected sample of certified Passive Houses across the country during the - winter season. The objective of this study is to compare inhabitants comfort to accepted thermal comfort standards and to verify building practices.. Thermal Comfort Passive Houses are typically designed to maintain a constant indoor temperature of F ( C), although some variation is expected with varying outdoor temperatures (this variation is limited to a ± F swing by Passive House standards). Physical thermal conditions of the various houses will be compared to the comfort range specified by ASHRAE Standard -, Thermal Environmental Conditions for Human Occupancy (). This standard states that the percentage of a buildings occupants dissatisfied with general comfort should be less than % (category A) and up to % (category C) in buildings with mechanical heating, cooling, and ventilation (). In a recent study of European Passive House projects, with more then dwelling units, not a single occupant gave a negative thermal comfort rating of their dwelling space (). In this same study, participants were asked if living in a Passive House was more or less comfortable then their previous standard construction residence. All the residents indicated an increase in thermal comfort in their new residence after staying through a winter, despite their pre-winter apprehensions due to a lack of radiators, which they were accustomed to in their previous residences. According to the CEPHEUS study conducted, residents typically set thermostats between F ( C) and. F ( C), and remained comfortable while the indoor air temperature remained between. F ( C) and F ( C). Residents were also highly satisfied with the even temperature distribution throughout the space compared to the stratification seen in normal houses ().. Indoor Air Quality Indoor air quality is often a concern for owners first learning about Passive Houses given the elimination of ventilation through infiltration that results from airtight construction; if not properly ventilated this can lead to sick building syndrome. However, in a European Passive House study, where all the dwellings utilized a heat recovery ventilation system, 9% of occupants rated the indoor air quality of their dwellings to be good to very good with no negative ratings were reported ().. THE PROBLEM & HYPOTHESIS The performance metrics this study will examine are temperature variations during the winter design week (related to occupant comfort) and annual energy use (related to annual carbon emissions.) This research is concerned with the following questions:. Do Passive Houses maintain an average indoor temperature of F ( C) during the winter design week?. Does the window wall of the primary living space maintain an indoor temperature swing of less than F above and below F ( C)?. Are people thermally comfortable in the Passive Houses? What changes, if any, have been made to their lifestyles? Hypothesis: Houses built to the Passive House standard within the U.S. will successfully perform to Passive House expectations in areas such as thermal comfort, indoor air quality, and energy use.
. METHODOLOGY. Building Selection and Permissions Owners of Passive Houses within the U.S. were contacted and invited to voluntarily participate in the study. Six houses have agreed to participate in the data logging; three sets of data have been received and analyzed at this time. Houses with analyzed data include the Eugene house, the Salem house, and the Chapel Hill house. Toolkits are expected soon from the Isabella house, Hudson house and Lafayette house. TABLE : PASSIVE HOUSE BUILDINGS TESTED HOUSE LOCATION HDD F AREA s.f. A Eugene, Oregon B Salem, Oregon 9, C Chapel Hill, North *, Carolina D Isabella, Minnesota 9**, E Hudson, Wisconsin 9***, F Lafayette, Louisiana 9 *Information for Raleigh, NC **Information for Duluth, MN ***Information for Minneapolis, MN. Selection of Measurement Parameters A building designed and certified to the Passive House standard is expected to remain at a consistent temperature between degrees (either higher or lower) of F and relative humidity within the range of -%. Temperatures and humidity levels were recorded in various locations throughout the home to verify the home s ability to stay within the prescribed range. As a control metric for the environment in which the house functions exterior temperature was also measured. Another criteria in the Passive House standard is the ability of the building to keep all surfaces within F of the ambient temperature. This is especially difficult to do with windows due to their higher conductance in relation to the rest of the building envelope. In order to test this criterion a system to compare the window surface temperatures against the wall surface temperatures was developed in which a number of measurements are taken along the window surface, the frame and a point on the wall one foot outside the window frame [Figure ]. In taking these measurements verification that each surface was within F of each other and ambient air was performed. Fig. : Temperature Measurement Points on Interior Window Wall Elevation Although the HRV or ERV brings in % fresh air indoor air quality (IAQ) is a concern in Passive Houses due to their airtightness. Testing the CO levels within the home allows users to determine if there is enough fresh air being provided to the space. A guideline of ppm of CO will be used to analyze house performance as it typically is used as a predictor of odors and bioeffluents and not as an indicator for health hazards (). When possible a years worth of energy bills were collected from homeowners. This information will be used to verify the Passive House claim of up to 9% space-conditioning energy reduction for houses built to this standard.. Toolkit Assembly and Training Protocol Toolkits were assembled and shipped to home owners. These toolkits included three dataloggers, one CO meter, one Raytek surface temperature gun, occupant surveys and an instruction sheet on how to use the tools for the study. The instruction sheet directed occupants to complete a series of tasks: place one HOBO datalogger (reading temperature and humidity) on the exterior or their home, place one HOBO datalogger (reading temperature and humidity) in the interior near the home thermostat, place one HOBO datalogger and CO meter (reading CO levels, temperature and humidity) within the kitchen; take surface temperature measurements of indicated locations of a window within the main living space [Figure ], provide one year of utility bills. In addition to setting up the tools all occupants within each house were asked to complete a brief survey on their comfort and behavior within the home.. Survey Development A question survey was developed regarding occupants perception of thermal comfort and indoor air quality within their homes. Although these homes may fall into
comfortable ranges by the Passive House standard an understanding of whether this resulted in a greater perception of comfort by the occupants was desired. Example questions of thermal comfort and behavior include: What is your thermal comfort within the primary living area at this moment? (Please select one) Cold Cool Slightly cool Neutral Slightly warm Warm Hot Right now I would prefer to feel: (Please choose one) Warmer No change Cooler. Analysis Procedure All data collected from toolkits was imported into Excel and analyzed with respect to ) whether the houses maintained average indoor temperatures of F ( C) during the logging period, ) if CO levels remained below ppm and ) if the surface temperature of the primary living space window wall was within F of ambient temperatures. The survey results were analyzed to determine if residents ) are thermally comfortable in Passive Houses, ) are satisfied with the indoor air quality provided, ) are satisfied with energy use expectations and ) the measures that are taken by occupants in maintaining a comfortable environment.. RESULTS & ANALYSIS. Thermal Conditions Example questions of behavior include: If you have felt too cold, what actions id you take to become more comfortable? (Select all that apply) N/A Turn on the heat Open sunshades Increase clothing Drink a warm beverage Move to a different room Nothing Other If you have experienced too little air movement, what actions did you take to achieve acceptable air movement? (Select all that apply) N/A Turn up ventilation system Open a window Turn on a fan Move to another room Nothing Other By including both questions about the environment and the occupant s behavior conclusions can be made about how the house operates and what measures users take to maintain a comfortable environment. Fig. : Indoor Air Temperature for the Eugene, Salem, and Chapel Hill Houses over week long testing period Figure illustrates the temperature fluctuation within the three homes tested through the week long testing period. The temperatures remained within the F to F range for most of the tested hours. Data from house C showed spikes in the kitchen temperature above F on several days. The occupants attribute these spikes to periods of heavy cooking and two evenings of houseguests. TABLE : INDOOR AND OUTDOOR TEMPERATURE SWINGS House Average Exterior Daily Temp Swing Average Interior Daily Temp Swing Max Indoor Temp. Swing in Hour Period A. F. F. F B. F. F. F C. F. F. F
Measurements from the two indoor data loggers were used to find the average daily temperature swings in the house through the week, shown above in Table. The temperature in the homes remained remarkably stable, with the average daily temperature differential between. F and. F. This is surprising because houses A and B rely on manually controlled space heaters to control the indoor temperature, rather than thermostat controlled heating. The maximum interior temperature differential within a hour period was also recorded. House B experienced a. F temperature swing over one period in which there was frequent cooking and multiple guests. TABLE : TEMPERATURE DIFFERENTIALS House Outdoor Temp [ F] Indoor Amb. Avg [ F] Coldest Surface Temp [ F] Temperature Differential A.9... B. 9.9.. *C... *. *Average of readings, one each day of testing. The location of the coldest surface temperature in Houses A (Eugene, OR) and C was the bottom of the window frame. The coldest surface measured in House B (Salem, OR) was the center of glass. Ventilation and Carbon Dioxide Levels Measurements of CO levels of all houses remained within safe levels throughout testing, generally remaining below the ppm guideline used in the study. These measurements suggest the houses ventilation systems provided an appropriate amount of fresh air supply and exhaust. Fig. : Humidity for the Eugene, Salem, and Chapel Hill Houses over week long testing period. The houses all maintained acceptable indoor humidity levels, with RH remaining between % and %.. Window Wall to Ambient Temperature The results of surface temperature measurements surrounding windows in the primary living area of the homes are shown in Table. The coldest surface temperature recorded was compared to the average indoor ambient temperature to find the temperature differential. The data shows the windows performing relatively well, through not always within the F differential target. House C (North Carolina) measured surface temperature approximately one hour after sunset for each day of the study week. Through the week, the coldest surface temperature reading ranged from. F to. F below the houses ambient average at the time of measurement. Each of these readings were taken approximately one hour after sunset on days with outdoor temperatures higher than winter design conditions. This suggests that temperature differentials surrounding the windows are likely higher on the coldest winter hours. Fig. : Kitchen CO for the Eugene, Salem, and Chapel Hill Houses over week long testing period. The two spikes of CO levels in House B again correlates with the weekend days which the residents cooked meals and had - houseguests. House A showed CO levels above ppm at the start of monitoring. After seeing the levels on the logging CO monitor, the homeowners increased their ventilation rate in order to keep the house below ppm.
TABLE : CARBON DIOXIDE LEVELS House Average CO Level Max CO Level A ppm ppm B ppm ppm C ppm ppm. Survey Responses Eight residents of Passive Houses have completed the survey. In addition to the owners of the three measured homes, one homeowner from Urbana, IL and one from Belfast, ME completed an online version of the survey. Four residents were male and four were female with two between -9 years old and six over the age of. If you have felt too cold, what actions did you take to become more comfortable? The following charts show responses of the thermal comfort portion of the survey. What is your thermal comfort within the primary living area at this moment? Fig. : Thermal Comfort survey responses Relating to the responses listed above in Fig., only two out of the eight surveyed would prefer to be warmer, while the remaining six prefer no change. Fig. and : Thermal Comfort survey responses Figure shows that occupants use both passive and active accommodations to feel more comfortable in their homes. The following charts show responses of the air quality portion of the survey. How would you describe the air quality right now in the primary living area? How often since November st have you felt too coldin the primary living area? Fig. 9: Air Quality survey responses Six out of the eight people surveyed reported there was never an inadequate amount of air being delivered to the home. One responded to rarely having too little air movement and one responded to rarely having too much air movement. No one reported experiencing any unpleasant odors and one reported experiencing a little air stuffiness. Dust was a more prominent issue for homeowners. As seen in Figure, seven out of the eight surveyed had some problem with dust.
Since November st have you had problems with dust? The monitoring of these three houses helps verify the success of the German developed Passive House standard and it s potential within the range of U.S. climates. The use of post-occupancy evaluation such as this can help to inform the use of existing houses and the design of future projects. Generally all homeowners reported satisfaction with their homes. Data suggests that the homes are performing to Passive House comfort principles during winter conditions.. ACKNOWLEDGEMENTS Special thanks to: Fig. : Air Quality survey responses The following charts show responses to the overall home performance portion of the survey. During one year of operation, you energy bills were: Fig. : Energy Cost survey responses In the houses surveyed, there were mixed results regarding the expectations in energy reduction. The owners of the house who reported their bills were higher than expected also were having a problem with their heating system, which may explain their higher energy bills. Beyond your home's primary heating source, how often have you needed to add extra heat within the primary living area, such as a space heater? Owners of all houses tested Passive House Consultants of all houses tested Graduate School NetZed Lab Passive House Institute US. REFERENCES. ANSI/ASHRAE Standard - Thermal Environmental conditions for Human Occupancy. Eicker, Ursula. Cooling Strategies, Summer Comfort and Energy Performance of a Rehabilitated Passive Standard Office Building. Applied Energy vol, issue, pgs -9.. Schnieders, Jürgen and Andreas Hermelink. CEPHEUS Results: Measurements and Occupants Satisfaction Provide Evidence for Passive Houses Being an Option for Sustainable Buliding. Energy Policy., Vol, N, pg -. Grondzik, Walter; et al. Mechanical and Electrical Equipment for Buildings: th edition. Hoboken: John Wiley & Sons, Inc.,.. Feist, Wolfgant, et. al. Re-inventing Air heating: Convenient and Comfortable Within the frame of the Passive House Concept. Energy and Buildings vol,, pgs -. ANSI/ASHRAE Standard - Ventilation for Acceptable Indoor Air Quality Fig. : Additional Heating survey responses. CONCLUSION