1、88 2009 ASHRAEABSTRACTCombined heat, air and moisture (HAM) simulation at the building envelope level and building simulation have been separate activities for many decades. In HAM-models, the indoor conditions are handled as known boundary values, while all building simulation tools predict inside
2、temperatures and net energy demand without much consideration for rela-tive humidity and air pressure gradients.Things started to change with airflow modeling. That step not only allowed a better quantification of ventilation related energy consumption but also permitted a refinement of the humidity
3、 balances in the building. However, at least two facts remained poorly exploited: (1) many air flows enter and leave the building across the envelope causing a complex pattern of in- and exfiltration, indoor air washing, wind washing and air looping; (2), moisture buffering in indoor finishes, furni
4、ture and furnishings delays and dampens the inside water vapor pressure response compared to the outside. Both phenomena may have an impact on energy consumed for heating, cooling and air conditioning and influence the indoor environmental quality, while humidity transported by the adventitious air
5、flows in and across the envelope could accelerate degradation. Analyzing both facts through whole building heat, air and moisture modeling and studying the impact on energy consumption, durability and indoor environmental quality were at the core of the annex 41 activity.INTRODUCTIONAlthough it is w
6、ell known that the heat, air and moisture flows (called HAM) generated by building use and entering from outside, that the HAM flows traversing the enclosure and that the HAM flows injected by the HVAC system are in permanent and mutual balance, simulation tools and designers hardly consider that re
7、ality. Building designs are scrutinized on energy needed for heating and cooling, while HVAC-systems are dimensioned to deliver the power needed to keep the indoor temperature at comfort level even under extreme outdoor weather conditions. Indoor relative humidity however is mostly kept free floatin
8、g, as it is perceived as being less important except when the buildings function imposes full air conditioning. Few designers detail the envelope taking into account the full hygrothermal load from inside and outside, while hardly anyone considers the whole heat, air and mois-ture balance that devel
9、ops between the buildings interior, its envelope and the outside environment. This is a pity as air pressure gradients inside the building and between the build-ing and the outside generate airflows that may change the heat, air and moisture response of the envelope and the building drastically, whi
10、le buffering effects dampen indoor water vapor pressure fluctuations significantly compared to the outside. Resulting air ingress, possible rain penetration and moisture deposits in the envelope could not only negatively affect energy consumption but also trigger the envelopes durability. Simultaneo
11、usly, inside relative humidity, if not well managed, may affect perceived indoor environmental quality and become a driving force for mold and dust mite infection.Clearly, whole building heat, air, moisture response has impact on human comfort, indoor environmental quality, energy consumption and en
12、velope durability, reasons why in 2003 an IEA-ECBCS Annex, termed Annex 41, Moist-En was initiated (Hens, 2003).IEA-ECBCS Annex 41 Whole Building Heat, Air, and Moisture ResponseHugo S.L.C. Hens, PhDFellow ASHRAEHugo S.L.C. Hens was a full professor in Building Physics, Performance-based Building De
13、sign and Building Services at the Department of Civil Engineering, Faculty of Engineering, K.U.Leuven, Belgium. He is professor emeritus since October, 1, 2008.LO-09-007 2009, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transa
14、ctions 2009, vol. 115, part 2. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission.ASHRAE Transactions 89STATE OF THE ARTBuilding modeling started in the fifties. From the begin-ning,
15、the objectives were quantifying the net energy demand, analyzing the ways that demand could be reduced by building related measures and getting information on the temperature without heating and cooling as this allowed evaluating over-heating. Later-on, HVAC-models were added and energy consumption
16、became the quantity focused on. Hardly any model, however, was able to quantify the air and humidity balances in the building. Instead rough estimates on infiltra-tion and ventilation were used and humidity remained untouched (ASHRAE, 2001)During the same period, the research effort on heat, air and
17、 moisture transport focused on the envelope. In the sixties, a few simple evaluation tools became popular. They scaled the moisture response down to one main probleminterstitial condensationand two steady state transport modesheat flow by conduction and water vapor flow by diffusion (Glaser, 1958, G
18、laser 1958, ASHRAE, 2001). Today highly sophisti-cated one- and two-dimensional full heat and moisture models are available that allow modeling vapor and liquid flow, that are transient in nature, that consider moisture sources such as wind-driven rain, rising damp, initial moisture, sorption and de
19、-sorption, interstitial condensation and surface condensa-tion. Some even allow quantifying some of the consequences of unfit moisture tolerance, such as hygrothermal stress and strain, mold infection, corrosion, salt transport and frost damage (Pedersen 1990) (Carmeliet 1992) (Knzel 1994) (Grnewald
20、 1997) (Sedlbauer et al. 2003) (Nicolai 2007). Examples of such models are: Match, Wufi, Latenite, Delphin and HygIRC. In Europe, the one-dimensional full models even became subject of a standard (CEN, 2003). All envelope models, however, take the indoor conditions (temperature, relative humidity, a
21、ir pressures) as known boundary values. This of course is fiction, except in case of full air conditioning, when the indoor environment is completely decoupled from outdoors. Also a correct implementation of wind driven rain and its impact on the building envelope remained a weakness. In fact, altho
22、ugh wind and wind driven rain have been a research topic for many decades, one had to wait until CFD became a commonly used tool before a turn was made from experiment and simple calculation to full simulation of rain loads on envelopes (Lacy et al., 1962) (Blocken et al., 2004).As said, the analysi
23、s of airflow patterns within a building was an important step on the road to whole building HAM analysis. Basic work on inter-zonal flow has been done by the Comis group and Annex 23 (Allard et al., 1990). The last decade, large numbers of researchers use CFD to analyze intra-zone flow (Baker et al.
24、, 1994). The linkage between the flows in the building and those in the envelope, however, is hardly established, although the study of air flows in and through envelope parts has underlined their importance for a correct evaluation of the hygrothermal response (Kronvall, 1982) (Trechsel ed., 1994)
25、(Janssens 1998).Finally, the last years, we saw a renewed interest in indoor moisture buffering by finishing layers and furniture (see Figure 1) (Svennberg et al., 2004). A few software packages have been developed, which allow evaluating the effect. Measurements on buffering capacity of finishing m
26、aterials and furniture were performed in several laboratories. Nordtest initiated a research program on the subject, included a round robin on buffering (Rode, 2003).ANNEX OBJECTIVESThe annex was meant to develop a holistic view on the overall HAM transfer between the buildings interior, the enclosu
27、re and outside. The two specific objectives were:1. Exploring the physics involved in whole building HAM response. That included basic research, a further devel-opment of models, measuring moisture storage in finish-ing materials, substrates, furniture and furnishings, mock up testing and field test
28、ing. Test results were used to verify and validate models by inter-comparison and confrontation with measured data. 2. Analyzing the effects of whole building HAM on comfort, indoor environmental quality, energy consump-tion and enclosure durability. The first objective focused on a better understan
29、ding of the overall HAM-flows that come from inside and outdoors under different weather conditions and their effect on the buildings overall hygrothermal response. The annex had no intention to develop an own, so-called reference whole build-ing HAM model. Instead, all participants were motivated t
30、o develop their own full or simplified models and to use the annex activity for refining these tools. Within that context, simplified modeling was seen as quite important as full tools are very demanding in terms of input and time consumed.A strong drive behind the second objective was good comfort
31、and good indoor environmental quality. Both deter-mine to a large extend building users satisfaction. In many climates, people in fact spend 80% and more of their time inside buildings, which means that the whole society is bene-fiting when comfort and indoor environmental quality are optimal. At th
32、e same time, avoided energy consumption is of great help in establishing the goals of the Kyoto and future post-Kyoto protocols. From that point of view, air humidity changes, which are termed as latent energy, play a significant role in hot moist regions, where latent heat often represents 50% or m
33、ore of the annual cooling load. Well balanced mois-ture storage in finishing layers, substrates, furniture and furnishings could reduce that percentage. On the long run, the result should be a net saving in energy resources, less CO2produced and added sustainability. Also a better durability increas
34、es sustainability. Longer service live of buildings in fact economizes on material use, embodied energy and embodied pollution. Hence, damage statistics learn that bad 90 ASHRAE Transactionsmoisture management is the most important cause of a too short service live, surely when considering the envel
35、ope. Objective 1 was translated in a set of original research tasks with a round robin on vapor permeability and sorption of painted and unpainted dry wall and model simplification, veri-fication and validation as kernel activities. Under objective 2 measures were studied as to moderate possible neg
36、ative effects of combined HAM transfer with correct moisture management, humidity storage, humidity controlled ventila-tion and better energy efficiency as some of the tracks followed. ANNEX ORGANISATIONThe work was structured in four subtasks:1. Modeling principles and common exercises2. Experiment
37、al investigation3. Boundary conditions4. ApplicationsEach subtask got one or two subtask leaders: Carsten Rode of DTU, Denmark, and Monika Woloszyn of Cethil, France, for subtask 1, Staf Roels of K.U. Leuven, Belgium, for subtask 2, Kumar Kumaran of NRC, Canada, and Chris Sand-ers of GCU, UK, for su
38、btask 3 and Andreas Holm of FiB, Germany, for subtask 4. They were responsible for the activity within their subtask and acted as editors for the final report on their subtask.ANNEX ACTIVITYWorking MeetingsOne three day kick-off meeting and eight three day work-ing meetings were organized:During the
39、 kick-off meeting, the Annex structure was created and all participants got the opportunity to present their experiences in the field of whole building heat, air, moisture modeling. Each working meeting had an identical outline: discussing the results of the common activity in each of the subtasks,
40、presenting free papers with new ideas, research results and deeper knowledge and planning for the next six months. From the sixth meeting on, more time was devoted to discussing the final report outlines and reviewing the text of Figure 1 Inside water vapor pressure in an office, comparison with the
41、 water vapor pressure outside. Without buffering, the value outside should never pass the value inside. It does, proving buffering is a fact.Meeting Place, dateKick off meeting Leuven, (B) November 26-28, 2003First working meeting Zrich (Ch), May 12-14, 2004Second working meeting Glasgow (UK), Octob
42、er 27-29, 2004Third working meeting Montreal (C), May 16-18, 2005Fourth working meeting Trondheim (N), October 26-28, 2005Fifth working meeting Kyoto (J), April 3-5, 2006Sixth working meeting Lyon (F), October 25-27, 2006Seventh working meeting Florianopolis (B), April 2-4, 2007Eighth working meetin
43、g Porto (P), October 22-24, 2007ASHRAE Transactions 91the reports. In all meetings, except the one in Montreal, all participants followed the activity in each of the subtasks. That way, a kind of common knowledge basis was created, which facilitated the discussions and the review process of the fina
44、l reports.ParticipationIn total, 113 people participated in all or part of the work-ing meetings. They introduced 269 free papers and worked on in total 11 common exercises.ANNEX RESULTSSubtask 1: Modeling Principles and Common ExercisesThat subtask concentrated on whole building HAM modeling with s
45、pecial emphasis on HAM-transfer between the outdoor and the exterior surface of the building envelope, HAM transfer in the envelope, HAM transfer between the interior surface of the envelope and indoors, HAM transfer from outdoors to indoors and vice versa through leakages, purpose designed ventilat
46、ion grids and air in- and outlets, HAM transfer between the indoor air, furniture and furnishing plus HAM transfer between the different zones in a building. The models that were verified and validated using the common exercises took into account parameters such as location and orientation of the bu
47、ilding, the HVAC-system, adventitious and user defined air flows, moisture response by hygroscopic finishes, furniture and furnishings, the type of room (bath-room, living room, etc.) and users behavior (number of people, activities that released moisture and heat, frequency and duration of window v
48、entilation). The schedule of common exercises looked as follows:Exercise 0 Dry BESTEST. Verification of the thermal part of the models by inter-model comparisonExercise 1 Wet BESTEST. Generating vapor in the BEST-EST building, prediction of the inside relative humidity in isothermal and transient co
49、nditions. Verification by inter-model comparisonExercise 2 Validating models by simulating experimental results at test room level under isothermal condi-tionsExercise 3 Validating models by simulating experimental results at test room level under non-isothermal conditionsExercise 4 Energy consumption in the test rooms used for the non-isothermal measurements, assuming a humidity controlled ventilation system. Verifica-tion by inter-model comparisonExercise 5 Real world case, evaluating the impact of adven-titious infiltration flows that traverse the envelope on durability and e
