Foam Insulation

[Deltarat]

I have a 30x50 pole building with metal trusses on 10' centers and 2x4 lathes on the edge between the trusses on 24" centers. I have the foil bubble wrap under the metal roof. The roof is vaulted with no ceiling joists. My shop has heat and air and I would like to add some additional insulation to conserve energy.

I was thinking rigid foam panels either cut to fit between the 24" lathes up against the foil insulation or across the lathes leaving a 3 1/2" dead air space between the two. I thought the rigid panels would be the easiest to install without having to cover roll insulation with a ceiling.

Would either of these be a good idea?

 

[rlitman]

The foil faced polyurethane foam panels offer more R per inch than styrofoam, but to get the absolute most out of it, you want an airgap of 2 to 2 1/2 inches. A 3 1/2" airgap is too big, and will actually hurt your insulation's efficiency due to the convection that will take place in that space.

 

[Deltarat]

I guess I could put them between the lathes and make them flush or a little below flush the get the right air gap depending on thickness of the panel

 

[BadgerBoilerMN]

It depends on where you are and the indoor design temperature. Air-gap pertains to reflective media exclusively. He already has the questionably "bubble-foil".

 

[Deltarat]

I am in Ms. with summer temps in the 90s-100 and winter 30-40. My heater will keep it 70 in the winter and the air will get to 65 in the summer, but they have to run several hours for either to get there. I was hoping for a quicker warm up and cool down and each to shut off more to cut the utility bill.

 

[BadgerBoilerMN]

Quick or efficient, you have to pick one. To save fuel and be comfortable you have to have at least 8 hours setback.

In most cases using modern construction, insulation is the key with a set it and forget it control. This is particularly true of air conditioning as the latent heat (humidity) is the most important factor in human comfort when things get hot. Naturally most of the stuff we keep in our garages do not like moisture.

75°F is considered cool in summer and 68°F warm in winter especially when the slab is radiated or physical work is involved.

 

[70 chevelle]

Deltarat,
how do you like the foil bubble wrap do yo think it made a difference

 

[Deltarat]

Deltarat,
how do you like the foil bubble wrap do yo think it made a difference

Yes, it makes a big difference, but I would like more. On a 100* day when you can not put your hand on the wall on the sunny side, it is cool to the touch on the inside.

 

[Deltarat]

Quick or efficient, you have to pick one. To save fuel and be comfortable you have to have at least 8 hours setback.

In most cases using modern construction, insulation is the key with a set it and forget it control. This is particularly true of air conditioning as the latent heat (humidity) is the most important factor in human comfort when things get hot. Naturally most of the stuff we keep in our garages do not like moisture.

75°F is considered cool in summer and 68°F warm in winter especially when the slab is radiated or physical work is involved.

I would not mind leaving the heat and air on all the time if it were not running full most of the time. Nether one of them cut off much when it is hot or cold outside. I just want more insulation so they will cycle some and lower the utility bill.

I agree that the air taking out the humidity makes a big difference in the comfort level here in the south. Being able to keep the skeeters out is another help with the comfort level.

Anyone else have an opinion on the foam?

 

[toyotadriver]

Deltarat,
how do you like the foil bubble wrap do yo think it made a difference

The foil wrap does make a difference but primarily in the summer time. In the winter, it does very little.

Foam is a GREAT insulator and in spite of what fiberglass proponents will tell you, if foam and fiberglass have the same R value, the foam will insulate better.

I installed 3 inches of foam sheets on my shop building roof. It is amazing how it stops heat loss/gain. Yet, it's only about R15. However, R15 of foam is FAR better than R15 of fiberglass.

Fiberglass is certainly better than nothing but foam beats fiberglass hands down.

 

[Deltarat]

Would you place it between the lathes up tight to the roof and foil or across the lathes leaving a 3 1/2" air gap between it and the foil?

 

[toyotadriver]

Would you place it between the lathes up tight to the roof and foil or across the lathes leaving a 3 1/2" air gap between it and the foil?

I would not leave a gap between the foil and the foam. If any moist air gets past the foam it will condense on the cold roof between the foam and the foil. Even if you place it against the foil, you should still tape all the seams because if you don't, moist air will still get past and condense.

I taped mine and then (when I am done) will cover the foam on the inside with a vapor barrier with all the seams taped.

If you can get air flow between the purlins, then you could leave the air gap but it won't be serving any insulating purpose. You still need to minimize the amount of warm moist air that is able to get past the foam.

 

[Jeanne95]

It depends on where you are and the indoor design temperature.

 

[Deltarat]

It depends on where you are and the indoor design temperature.

I'm in Ms and desire a temp of <70>*