![]() So, if you take a temperature like the 1% annual heating design day, you only have 3 days of the typical year when the temperature is below this value. To get conditions that approximate steady state assumptions like those of THERM, you really need a full 24-48 hours of steady conditions on the indoors and outdoors for thermal gradients to develop across construction assemblies. Speficifically, it’s very clear from trying to approximate steady state conditions in the real world that real buildings are in a constant state of flux as outdoor temperatures go up and down and the sun rises and sets. I see has done an awesome job explaining the reasoning behind the condensation risk methodology and I just wanted to add that my one experience with controlled physical experiments gave me a lot of insight into the relevance of steady state models like THERM. We even did laboratory experiments, and wait for it, built test , It seems quaint considering what we do today, which is pretty much sit at the computer, but in the old days we would actually go out and look at real walls an measure them in situ. How do we know they give the right answer? Easy, the real world tells us that they do. ![]() “notice that we are using “average monthly temperatures.” Why average temperatures? Ah, because they seem to work and give you the right answer. To account for storage, it is recommended to use average values (e.g., monthly average temperature) rather than more extreme design temperatures." Experience shows they play a significant role in heat and moisture performance of assemblies. 'Heat and moisture storage effects are not included in a dew-point analysis. The 2017 ASHRAE Handbook - Fundamentals include this brief statement in Chapter 27: Regarding the monthly mean versus minimum, I believe this is the original methodology in The Glaser method. The placement of the air barrier is more of a design detail and construction quality concern. The standard indoor air boundary layer in THERM is sufficient for your thermal transfer from indoors to the first layer of material. Designers cannot afford to ignore the risksĪssociated with surface or interstitial condensation.Hi will not need to model the air barrier in THERM since it does not posses any thermal resistance and THERM does not model air leakage. Have a condensation problem at some times. With the improvement in insulation levels, itīecomes more and more important for designers to be aware if their
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |