more garage insulation questions...

[Chang-kuao-lo]

i got my toy shop assembled, and now i'm getting to work sealing it up, and insulating it. i'm going with a reflective barrier (basically bubble wrap with mirrored mylar on one side) and nothing behind it. it's all steel construction, and the reflective barrier seems the way to go as it doesn't promote condensation, which can be a big problem as the humidity here tends to be a bit on the high side. my question being, should i do a gable vent or just leave the gable ends unsealed to promote a bit of airflow behind it, or am i just as well sealing the whole outside sheathing?

 

[nomembername]

Gable vent. That way you control where airflow is, and sealing the rest of the gable panels prevents unwanted moisture (and bug) intrusion.

 

[se2000]

I'd use some high density foam board with foil face. do yo plan an airspace between the insulation and outside skin? if so you will need a vent

 

[Madogeoff]

Chang,

Even if you 'seal' the shop in reflective mylar and bubble wrap, moisture, (condensation) will still form in the rafters because of the temperature differences that arise daily between the outside of the roof, gables and inside the roof area., and rising hot air. The principle is that a heated building should be vented to displace the moisture and sometimes extreme heat that can collect in the joist areas to protect against rot. Whether you vent both gables or put vents on the roof is a matter of preference.

Further I would suggest more insulation in the walls as it not only helps retain heat in a building, but also coolness during hot weather.

Anyhow, I cannot be more specific not knowing the size and structure system of your metal building, and I think if you were to get a copy of your local building code specifications you would find all the details you need, unless it is a unique construction.

All the best with your shop

 

[Chang-kuao-lo]

this is the manufacturer's recommended type of insulation, the fellas who put the thing up said that it's the way to go with an all-steel building. instead of a gable vent, i am leaving the 1/2" gap at at each gable end between the wall and the roofline. later, i'm going to stuff a screen in there to prevent any unwelcome guests. the idea is that it being a reflective barrier, it will prevent 95% of radiant heat from passing and conducting it out to the steel structure. we'll try it out and if worse come to worst, i can fill the whole works with blown-in loose fill, or foam, or what have you. as it stands, spray-foam was going to run ~$1,500, rigid foam board ~$1,000, and the reflective barrier came in at ~$500.