18X20 - Insulation Reccomendations

[tbgallant]

Hi guys, I'm new here. Stumbled upon the site and think it is just great! I finally have a garage after 10 years (since I was 16) friggin' around with old cars in the driveway or other folks garages (always in a hurry to get things done and out of their way, no fun!).

It is a small 18X20 detached garage, single door (with a man door). Single window as well. It came 'as is' when I bought the house. It seems to have been built 'ok'.. the finish on the inside was never done.

It is 'mostly' insulated. I've taken some pictures (and can take more for clarity) of the current situation. Please comment on anything you see here that may catch your eye as being good or bad construction practices (all done by previous owner, I haven't done anything yet, ha).

Also I plan to fill in the gaps with pink insulation on the walls, add poly / vapor barrier where it isn't already and finishing the walls with something.. possibly pine boards.

I had planned to just to staple up some poly on the ceiling and replace all the white foam with pink insulation. But after reading a bit, this white foam stuff might not be that bad?

What would you reccomend I do to get the best insulation in the roof/attic area?

The cross 'beam's seem to be 2X6' or 2X8's. I will be using the attic for light storage (nothing heavy, but bulky). There is a large ~4'x4' hatch that swings downward. I plan on 'sticking' some insulation on top of this as well (none currently).

Lastly, I'm curious to hear any comments regarding attic ventalation. There are vents front and rear at the peaks (you can see one in the last picture). There is also a 'twirling' vent at the center peak as seen below:

This seems like a lot to me, and potentially bad as it might **** heat out of the workspace with so much on a windy day? Shall I leave it as is, or block one off.. or??

Thanks for all the help. I'm new but very willing to learn all about the best practices for this type of stuff.

 

[kbs2244]

Leave the vents as is. Just be sure no rain can get blown in. You want the attic above a heated space to be at outside temp with plenty of air movment to get rid of moisture. You should have vented soffits. Do not cover them with any insulation. You problem is going to be not so much losing heat in the winter as it is getig rid of it in the summer. That is why your wirlly gig thing is there. To get rid of summer heat.
Since the foam board is there, use it. Maybe some battens across the celing to hold it up better. Do fill in upstairs where there is no insulation. Same with the walls downstairs. Don't worry about poly sheeting. If you pink stuff has the brown paper on it, that is enough. Unless you are going to wash your cars in there in the winter with the door closed, you are not going to create that much moisture.
But I am not a fan of tightly sealed garages or shops. We do things in them we would never think of doing in a home. (I guess that is why we have them) Things that smell, have dangerous fumes, etc. You may waste some heat but keep some freash air coming in and bad air going out when you are working.

 

[tbgallant]

The 'siding' on the underneath of the soffits have a bunch of little holes in them (you can see pictures in the 'chimeny for a woodstove' thread I started). I'll assume those are the vents. so I want the edges of the 'ceiling' to be open air to the attic?

I will fill in the gaps in the attic with pink. Can I just stuff it in the cracks between the foam board?

Also, is the R-value of the foam board good enough? I forgot to mention that I'm in eastern Canada (cold days are -10/-15C (50-60F)). I would say most of the foam blocks are ~ 4-5 inches thick. I don't have a problem investing in some more fiberglass batts to lay on top of the foam if it isn't overkill?? Just reg R-15 stuff (same as I will put in the lower 2x4 walls)?

You talk about not needing poly. Not all the pink has the brown paper on it, so I'll need to poly those before adding the wall covering right?

Also, won't me leaving the poly off the ceiling let alot of cold drafty air circulate down (and hot air circulate up and out?) if I don't seal the bottom from the attic?

I plan on keeping the garage heated all the time with a 4800W 240 V electric heater to just above freezing of to prevent freezing of liquids and condensation/etc from rusting my tools.). So I was thinking I'd want it as tight as possible. This make sense?

I'll be using a woodstove when I'm in there working, and will have excess heat then and can always crack the window/door to get proper ventalation during any welding.

Anybody else have any comments? Trying to make this really efficient so I don't waste a lot of electric heat ($$) when I'm not in there working.

Thanks so much.

 

[tbgallant]

Don't take this comment the wrong way, but can anybody reccomend any other 'heating / construction' type forums I can post the above questions?

I really don't want to waste time and money doing it the 'wrong way' and I really have no idea what the 'right way' is.

Thanks

Tim

 

[kbs2244]

If the foam is 4 inch or more thick, it is fine. Again, don't worry about the poly. Poly is for a moisture barrier. Garages do not generate the moisture that houses do, unless you wash the car in them. In a house, you are taking showers, cooking, have dishwashers venting, etc. And you keep the doors shut tight. You don't do that kind of stuff in a garage and you open a pretty big door pretty often. They get aired out.
I think you are overly concerned with heat loss. Poly will not stop heat loss. Use the pink stuff to fill in the obvious lack of insulation spots. Wait for winter and find any cold spots to fill in. Foam, like Great Stuff, is what you want for some of those smaller spots.
The attic over a insulated celing, covering a heated space, should be at outside temp. And vented to keep the air moving. Cover the door in the attic floor with insulation for heat rentention. But the attic itself should be cold.
Check out youe house. You will find moisture protection on the warm side of the wall, Kraft or poly, but not in the celing. You want any moisture that works it's way up there to perk through the insulation and get pulled out through the vents.