Another insulation question doubling up?

[Soccer918843]

So I have a 30x52 new build garage I plan on using rock wool r23 in walls and rock wool r30 in ceiling would 1.5” foam insulation be worth it on the exterior for the added cost? Will it pay for itself with the heat savings?

 

[68sixspeed]

The payback could take a while, I have a 30x50 with 13ft ceilings, same insulation specs, I keep it 58 degrees all winter and then bump it up if I'm going to be out there working, I burn less than 200 gal of propane a winter to heat it with a hanging modine heater. Usually 125-150 gal is a normal winter, 200 on a bad winter or if I'm working out there a lot. One thing I think helps is I'm not putting a cold truck in/out everyday, this is a detached garage more for projects not daily driver use.

I'd recommend investing in the best overhead doors you can afford and put the money there and sealing around them as well as a quality window and sealing those as best you can. I figued R30+ walls are not going to be that big a help with two 10x10 overhead doors with R16-R18 max.

 

[u2slow]

IMHO, not worth it. Insulate the ceiling better.

Board insulation is spendy for its R value. I'm using it under siding because my existing walls are no better than R10-14 or so.

 

[tonyciambrone]

IMHO, not worth it. Insulate the ceiling better.

Board insulation is spendy for its R value. I'm using it under siding because my existing walls are no better than R10-14 or so.

Agreed here- R-23 in the walls is good. r30 in the ceiling is not ideal. For Upstate NY i think you would be looking at R-49 to meet most codes/ recommendations

 

[Soccer918843]

What size hanging modine did you get?

 

[The Cobbler]

I'm in the more insulation in the ceiling camp.

 

[Soccer918843]

Agreed here- R-23 in the walls is good. r30 in the ceiling is not ideal. For Upstate NY i think you would be looking at R-49 to meet most codes/ recommendations

How would I achieve r 49? I have attic truss and only have 7.5” to insulate the height of the bottom of the truss and floor will be on the ceiling in the garage and another floor in the attic.

 

[nadogail]

I am in the more insulation you can get, the better your efficiency will be.

 

[Bert_]

Bigger thing is to air seal. All the r-value in the world doesn't mean squat if air can blow through it.

If you tape all the seams of the foam board that would air seal. But it's far from the only way.

 

[Soccer918843]

Ik spray foam is the best way but I can’t pony up the 7k to insulate if it was a house I would but a detached garage I can’t get myself to spend that kind of money

 

[theoldwizard1]

So I have a 30x52 new build garage I plan on using rock wool r23 in walls and rock wool r30 in ceiling would 1.5” foam insulation be worth it on the exterior for the added cost? Will it pay for itself with the heat savings?

Yes, it will pay for itself. The question is how many years !!

Starting with R30, I don't think it is worth the cost.

 

[toyotadriver]

YES to rigid foam sheets on the exterior. Upgraded insulation pays off. Rigid foam on the exterior does something batt and even spray foam can't do...it slows the heat gain/loss from the thermal bridging of the studs.

I built a house with metal siding and before we put the metal on, I had 1 inch foam sheets put over the exterior. Payback time was about 3 years or a little less. We plan to live here for a long time. Our utility bills are very low and will remain low.

 

[jabin]

YES to rigid foam sheets on the exterior. Upgraded insulation pays off. Rigid foam on the exterior does something batt and even spray foam can't do...it slows the heat gain/loss from the thermal bridging of the studs.

I built a house with metal siding and before we put the metal on, I had 1 inch foam sheets put over the exterior. Payback time was about 3 years or a little less. We plan to live here for a long time. Our utility bills are very low and will remain low.

Like putting a coat on to cover everything vs sticking insulation between your ribs. But it would also pay a lot to put a hat on since a lot of heat loss is via the roof.

 

[68sixspeed]

What size hanging modine did you get?

sorry for the slow reply, Modine 125k btu, it's a bit oversized but the recovery is awesome if I go out and need to bring the garage up to working temps.

 

[tonyciambrone]

How would I achieve r 49? I have attic truss and only have 7.5” to insulate the height of the bottom of the truss and floor will be on the ceiling in the garage and another floor in the attic.

Ok so more information is probably needed about the construction and layout...What is the truss construction like? What is the spacing? Is the roof just steel over purlins, or is it sheathed? Are you venting the 'attic' or sealing and conditioning it? etc