Insulation questions?

[lethallyinjected]

I'm sure it's been beat to death... I searched, and there's a lot of bits of info here and there but not a good in depth source. Just closed on my first home, and I'm looking into insulating the garage ceiling. R values, vapor barriers, venting... I'm a complete newb as far as this stuff. Does anyone have a good step by step process for this? I thought I was just going to get rolls of 15inchx25 foot insulation in R(recommendations on value?), roll them into the spaces, and be done with it. I've seen talk of needing ventilation/airflow in the attic, so many inches of airspace above the insulation itself, vapor barriers... any help would be appreciated. For reference, it's a 3 car garage, and I'm in Oklahoma so it can get to 110+ in the summer or as low as single digits in the winter. I don't have any real plans of heating or cooling, just trying to make it as nice as possible without spending a huge amount of $. Thanks.

 

[Falcon67]

Freak not. I'm only a few hundred miles away from you. If it's already a finished ceiling, just put as much insulation as you can afford up there. I have R13 bats installed after the ceiling, just laid into the stud bays. I usd kraft faced and laid the insulation kraft side down. If you are not living in it in this climate, that's as technical as it gets. I'd have used R30 but did not have the budget for that at the time, and could do the whole thing in R13. I'll do more later. R30 is real good, R19 decent, R13 minimum. I have not run the heat in the shop in two days and was just out there. It's 59F.

As for venting, do something to keep air moving above the insulation. Usually that would be vents in the soffits and something up high, either a ridge vent or regular passive vents near the roof ridge. Kinda depends on the construction of the garage. A building wiith gables could be vented in other ways. For our climate, I'm more concerned about bleeding off heat than any thing else. We have more of that than cold, for sure. It'll be 24 tonight but back to the 70s on Saturday. I used 10 soffit vents ( 5 per side) and 5 9" diameter passive vents on the back side of the roof.

 

[lethallyinjected]

Thanks for the quick response. I forgot to mention it's an attached 3 car, and it's a new home, so whatever ventilation is standard on the typical new home is what it has. I'm sure it helps a lot with keeping in heat, but I was kind of under the impression it would help keep it somewhat cooler as well? It's gotten so damn hot lately though, I'm kinda skeptical that it can keep it cooler as well. One friend seems to think it will make more or less no difference, but I disagree.

 

[Riverrojo]

Is your garage attic space connected with your house attic space? If so, you should have adequate flow. I added a few extra soffit vents to mine anyways (garage and house share attic space). I had r13 rolled above my drywall ceiling (garage and house). When my dad and I blew in r60 above the house, I added about 6 inches to the garage. It's about 25* right now and the garage is at 60*. House is only at 68*

 

[lethallyinjected]

Yes, garage and house share the same attic space.

 

[Oldbear]

We added a sound barrier wall between the attached garage and house (about 9ish inches thick now). We had R24 (6ish inches) and had more insulation blown in - up to about R50 or so - holds in the heat, eliminated drafts, and really cut down on noise. It should keep out what little heat we get in the summer.
The sound deadening is important as our bedrooms are against the garage... too much noise means waking the kids... which means I'm in trouble.

 

[lethallyinjected]

Forgot to ask, is there a certain type of insulation I should be looking at other than the R value?

 

[rebelranger]

Ok here is a great article. http://www.buildingscience.com/documents/reports/rr-0906-field-monitoring-hygrothermal-modeling-basement-insulation Basically explains what is best for which situation in walls. If you can apply these same effects to an attic however natural, not forced, ventilation is a must.

 

[Falcon67]

Our attached 2 car is not insulated overhead, but then I don't do work in there so I don't care. Plus there is a **** load of **** in the space above. This is SOP on most houses here (no insulation over the attached garage space).

You WILL benefit from insulating up there. The shop I built uses HardiPanel concrete board siding. When the west wall was painted red, it would hit 180F in the summer afternoon. With R13 and 7/16" OSB on the wall, the inside wall temp would be 95F with no AC running in the shop. During this last summer, the max it got in the 24x40 building would be 95~98, closed up, no AC. The house garage would be 100~110F easy.

 

[jimbbski]

I have a 2 car attached garage with two walls ajoining the house that are insulated and warm on the house side, the other two sides are of course the gagage door, (Insulated steel door) with the last side uninsulated. All of the walls are covered with drywall. I also insulated the ceiling with a R24 fiberglass insulation.

Living in the Chicago area we can very cold here. That being said my garage never gets colder then 30 deg. inside unless it gets below ""0" outside. Most of the time is more like low 40's to high 30's.

Turning on my topedo heater for 30-40 minutes will bring the garage up to about 70 degrees. I like to do this and then turn down the heater to say 60 and use an infrared heater as a spot heater while the rest of the garage cools back down to 60. On warmer winter days the main heater never comes back on.

 

[joshmodelskidoo]

you can do blown in or the rake in stuff but if your only heating or cooling on occasion i would just get some rolls of the cheapest stuff you can find. r13 at lowes is $10 for 25ft

 

[lethallyinjected]

Awesome, thanks guys. Really sounds like it's that simple, I'm garage/home attic all shared space so ventilation and what not is proper. Roll/blow in what I see fit and go. I'm probably going to do the rolls and call it good.

 

[willymakeit]

Make sure to put a walk board or something to avoid falling thru ceiling. Its better than trying to balance on the joists.

 

[ludakris04]

Make sure to put a walk board or something to avoid falling thru ceiling. Its better than trying to balance on the joists.

agreed... in my last house I had ripped down some plywood to slip through the attic opening.. worked out great...