Lack of sensitivity

uetzcayotl2012 · Posts: 4

I insulated the roof. 2.5 inches of EPS Polyestyrene (0.046 W/m2-K). Very little changes. 10 inches, almost the same results as 2.5"

I attach a graphic where I calculated the average day for summer. They are inside air temperatures. Blue line is the base case. Red is for 2.5" (it's under the green line) and green for 10" !!!

Another person at the institute tryed also using polyestyrene, but not from the DB data, he himself introduced the values. The builging he simulated has nothing to do with mine. Even the weather files are quite different (mine very warm and dry and his file is cold in winter, hot in summer, very humid). His results have the same problem: No sensitivy when using isolating material, no matter what the width is.

What happens?

Carlos

AJ Lester · Posts: 84 Location: Auckland

Hi Carlos,

Depending on the other materials used in the building, the weather file etc. you may find there is little or no difference based on the insulation installed in the roof.

My experience has included several buildings of this type, where, depending on climate, the temperature and energy consumption of HVAC are more or less entirely driven by internal gains. Insulating the walls, even with (riduculously) huge amounts of insulation makes little if any difference.

What are the parameters of your simulation? Would you care to post the simulation in order to have someone take a look at it?

Andrew Lester

Carlos · Posts: 25

I attatch the file with 1" isulation on roof.

Carlos · Posts: 25

Sorry,

I think I found a satifactory answer considering the effect of insulation only works with HVAC conumption, not with non-aconditioned buildings, because the inside temperature is too much close to "sun-air temperature" in this kind of climate. Right?

What would mean that many bioclimatic techniques might help reducing HVAC energy conumption, but do a little for reducing the air temperature if not conditioned.

Carlos

lklawrie · Posts: 76

It depends. In some of the US Southwestern states, a heavy (i.e. concrete) uninsulated wall is very effective in being able to extend the cooler night time temperatures and, in those cases, a more heavily insulated roof would help maintain that temperature.

And, yes, cooling by HVAC or mechanical means would be reduced here as well.

There are other climates where the night time temperatures (or other conditions) would not be sufficient to really help the daytime temperatures or reduced cooling/heating.

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