Attic Insulation

[Krfjkm]

Continuing the work on my garage- this is the attached garage for our daily drivers and not my shop.

I have all the drywall removed and plan to insulate from below as we have the garage attic floored and can’t do blown in insulation.

Any thoughts from you guys on what I should use or do to get this done?




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[loganb]

How much space is there to fill and how were the interior temps before?

 

[JunkBonds]

You can insulate the attic from the roof. Cut in vents, blow the insulation in then put the vents on.

 

[pattenp]

Faced fiberglass batts.

 

[Krfjkm]

Faced fiberglass batts.

That is what I am thinking— put faced insulation between the joists— need something 23” wide.


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[The Cobbler]

23" wide would be 24" center insulation .

 

[PWilks]

Fiberglass batts is probably the most cost effective way to do what you’re talking about.

your limiting factor is your truss bottom chord which is probably a 2x4 or 2x6, so it’s less the adequate.

If lumber prices weren’t astronomical I’d suggest sistering a 2x2 to the bottom of each truss for some added depth. All depends how you intend to condition the space and how often.

 

[James-W]

If the cost of spray foam is in the budget I would go that route. It would cost more initially but down the road it would save money on heating/cooling costs.

 

[nadogail]

As stated above you can sister the chords of the existing trusses to gain space to add faced fiberglass. The limiting factor will be how much are you willing to lower your ceiling hight.

 

[Krfjkm]

Thanks guys! It’s just a garage, but it does get hot and is the primary path for us to go into the house. It had zero insulation before so anything will be a big difference!

 

[CombatNinja]

Are you going to HVAC the area you are insulating?

 

[dlwilson]

If the cost of spray foam is in the budget I would go that route. It would cost more initially but down the road it would save money on heating/cooling costs.

I recently had 5" of spray foam put in my 24x40 garage (no attic floor) for $1800, and it works great. I used to open the man door and get a blast of hot air to the face (south Florida). Now it is ambient temperature. I have a mini split, and now it will cool the garage in 15 minutes. Big difference.

 

[NUTTSGT]

Id put in fiberglass batts of R13 with a 2x4 bottom chord, R19 if you have 2x6 bottom chord. Once that is done add 3/4"-1"reflective foam screwed to the bottom for more R value. Then add a ribbed metal ceiling.

Wait, this is attached, probably should have drywall.

 

[jrsavoie]

If the cost of spray foam is in the budget I would go that route. It would cost more initially but down the road it would save money on heating/cooling costs.

This. I would put visqueen, cardboard, compatible board insulation or something up against the floor and have the spaces spray foamed with 2 lb. Density foam. I don't know if the kits have gone up in price with covid. But that would be an easy do it yourselfer.

 

[rayra]

spray foam is no gain in R value in a 2x4 space, iirc it's R-13, same as glass in that depth of space.
OP if you are hanging drywall again, unfaced batts are fine. R-13 if 2x4, R-19 for 26, Don't try to cram more in, you just decrease the efficiency.

 

[K'ledgeBldr]

spray foam is no gain in R value in a 2x4 space, iirc it's R-13, same as glass in that depth of space.
OP if you are hanging drywall again, unfaced batts are fine. R-13 if 2x4, R-19 for 26, Don't try to cram more in, you just decrease the efficiency.

Yeah, if you’re talking “open cell” foam. Open cell has a 3.8/inch R-value. But closed cell foam has a R-7/inch rating.