Insulation Advice

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Forum topic by rockindavan posted 12-16-2012 02:11 AM 1109 views 0 times favorited 4 replies Add to Favorites Watch
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299 posts in 2637 days

12-16-2012 02:11 AM

The winter has finally come and nobody wants to work in a cold shop. I got a heater, but it only seems to be able to maintain a temp about 20 degrees above ambient. I’m a little worried that once it gets down to say 0 that the garage will never get above freezing. Instead of getting a bigger heater I would like to keep the heat I am putting out.

The garage is a two car, but is divided down the center with a stud and plywood wall. It is a rental so someone else has that stall and is unheated. The walls are brick and uninsulated. The garage door is crap. The garage roof has a 8’ peak. I put plywood and stairs in for storage, so it is a triangle type area.

So my question is where should I put my efforts to retain the heat. I could insulate the joists between the attic and ground floor. It seems that a lot of the heat just heats that area. Or I could insulate the roof, although it doesn’t keep the heat where I want it. I also plan on putting some rigid foam on the garage door. Insulating the walls won’t happen since I already have shelves and such mounted to them.

So if I insulate the roof or ceiling, does it matter what type. Can I use unfaced fiberglass or should I use faced. The only advantage I see is the resistance to dust. I’m not too worried about moisture because I only plan on being here for 2 years and I will probably tear it out when I leave. Or could I use rigid insulation between the joists.

I also want it to be as cheap as possible because it is a rental and I will really only get two winters out of it. Any input would be appreciated.

4 replies so far

View RonInOhio's profile


721 posts in 2865 days

#1 posted 12-16-2012 04:51 AM

Insulate whatever is directly above . That is where most of the heat is going.

Rigid XPS 2” (R13) Foam is around 40 dollars for a 4×8 sheet. So financially, FG may be the way to go .

If you are going to be making any significant amount of sawdust , I would suggest getting backed FG or putting up poly vapor barrier over the FG.

Not cheap but you could also cover the brick/concrete walls with fanfold xps, or that Reflectix product that is a foil vapor barrier designed for radiant floors. It would help reflect the heat back into the room. Just a thought.the Reflectix comes in rolls of varying sizes. I think a 4’ by 25’ roll is around 30-40 dollars.

1/8 xps fanfold is cheaper and I think would cover a larger area.
The R value of the Reflectix is around 3. The fanfold R is around 1. What warm air isn’t going through the ceiling you are probably losing into the uninsulated brick walls.
While those R values aren’t huge, it could make a dramatic difference on top of the brick.

View Kindlingmaker's profile


2656 posts in 3527 days

#2 posted 12-16-2012 05:02 AM

The 2” foam insulation from the big box stores is rather cheap and works vary well. We have cut and screwed it to the garage doors and the walls and ceiling are just as simple. Use long dry wall srcews and fender washers so I you move you can un-screw the insulation and take it with you…

-- Never board, always knotty, lots of growth rings

View Ted's profile


2847 posts in 2212 days

#3 posted 12-16-2012 05:13 AM

If you insulate between the rafters you will have to provide ventilation to prevent ice dam from forming.

If there is no real reason to keep the storage space warm, then insulation the joists between the storage and shop will be your best option. Also, if you have an opening going up to the storage space, you’ll want to close it off, as I’m sure you know heat rises.

Fiberglass – faced or not faced – is your best choice, as it will fill the space better. Anything rigid you would have to cut very precise for it to be at all effective.

Insulating the brick is probably not worth the hassle and expense. What would make a big difference is sealing any holes or cracks where cold air is getting in. Just stuff it with caulk, insulation or whatever is handy, to stop any air flow.

The insulation on the garage door will make a big difference. It might not be so easy to seal any cracks or gaps there, because of moving parts, but anything you can seal will help.

-- You can collect dust or you can make dust. I choose to make it.

View OnlyJustME's profile


1562 posts in 2378 days

#4 posted 12-16-2012 05:18 AM

Could also look into Roxul insulation. Since it’s fire resistant, water repellent and sound absorbent, it’s a better choice. Don’t know about price. Be careful with exposed rigid insulation. Fire hazard and gives off very toxic fumes if melted/burned. By code it needs to be protected from fire usually with sheet rock.

-- In the end, when your life flashes before your eyes, will you like what you see?

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