explain R value on garage doors. comparing options.

[Bad00SS]

I have narrowed down the doors to the brand and style of door and windows I want. Now they offer 3 insulation options. One is R7.94, one is R9.65 and lastly R17. Now the R17 is $3,000 upgrade to do all 3 of my doors. that is out of the picture. Now the difference is $1,500 to go from R7.94 to R9.65. would you even notice a difference? I'd rather save $1,500 if I wont see a savings in the heat bill. I will mention I am near Chicago and winters here do get cold and snow. I have read that the first 5 or 6 numbers in R value make the biggest impact on keeping heat in. anything after that the gains diminish at a certain rate and eventually it makes no difference like at an R40 your prolly maxed out. How true is this? someone explain how this works. I just cant justify spending $1,500 for 1.71 gain in R value unless someone shows me new information.

 

[Showkey]

In the math % change calculation it 21.5% increase. Plus the door surface area should be considered. Each single door would 75 sqft or more ?

Is the garage heated or are you just trying to hold heat from the attached structure?
Similar discussion occurs with windows. The insulation has more “value” as the temperature differential increases.


There are dozens of R value calculators free or paid.
This One calculates the effective R value and allows you to see the change with changes in construction or materials used:

https://www.rdh.com/new-construction/r-value-calculator-app/

Changing the window value in the default calculator would be similar to changing the garage doors R value. The setting for % of wall vs “window” setting would be critical as the garage door is large % of the wall. The closer the door R value is to the wall R value is important.

 

[Bad00SS]

The garage has a furnace in it. it stays at 55 degrees all winter. There is 1,416 sq ft of wall space total if there were no doors. The garage doors take up 340 sq ft of that wall space. that is 24% of the wall space taken up by doors. I guess that is quite large but I don't know how bad it really effects things.

 

[Showkey]

True..........not an easy calculation..........the fit and seal to the frame of any door is another important factor.
Low end and high end materials are rarely the best value compared to middle for the road specification.

Ball park to heat the garage space with NG, I would guess $30-50 per month for 7 months. 10% savings per month is $3-5. $1500 divided by $5 is 300 months. He savings could be greater because a poor grade of door might be the greatest heat loss in the garage. 20-30% changes the numbers in favor of a higher grade door. There’s a the comfort factor if you using the garage as work shop.......cold drafty door not desirable.

Propane heat ? Would change the payback number and cost of heating number.

 

[Bad00SS]

T

Propane heat ? Would change the payback number and cost of heating number.

natural gas furnace.

 

[Marctrees]

Bad - You may know this but be aware what the interior finish cladding over the insul is.

Less expensive is somekinda plastic... more expensive is steel.

More important then the door R itself is the quality of the installation ... full good weatherstripping AND installer that knows to make sure to adjust the door properly to take full advantage of the sealing.

Marc

 

[Bad00SS]

I chose the R7.94 and had a professional schedule an install. The R 9.65 door did have steel on the back instead of the plastic type stuff but I still couldn't justify the cost.

 

[D45]

I have three insulated doors, all Clopay

All are steel with polystyrene R-values of 8.4

Works well

 

[Toomanytools?]

Badd00ss:
I think that was a good choice don't think you would notice the 1.7 difference. The bigger benefit would be a door with no windows, and seals that keep the air movement out.

 

[dcg9381]

Let me throw this at you. First, I'm assuming these are "steel building" type doors, not your typical panel-based garage door.

I have 14x14' doors on my building. They are the roll-up type, probably R5.
The issue (for me) isn't really with the R value of the door. My doors are kept from direct sunlight by overhangs.

The issues with these doors are three fold:
1) The framing, track system, etc - tons of air.
2) They did not come with weather strip - I had to add it
3) They **** when it is windy. They rattle within their tracks and make noise. When it's windy, it's impossible to sleep in this building.

If I had to do it over again, I'd buy a panel-based door with a higher R value... Mainly because the flat panels can seal better against weather strip and they don't "rattle" around as much....

I'd go look / touch a few installed doors if you can...

 

[strutaeng]

I don't know anything about insulated garage doors, but:

To answer your question, you need to run a U-factor for the entire wall. U-factor is the inverse on the R value, i.e., R = 1/U. There's an article that explains how an un-insulated roof ladder hatch brings the R-value significantly of an attic:

https://www.energyvanguard.com/blog/34932/Attic-Stairs-A-Mind-Blowing-Hole-in-Your-Building-Envelope

It should be similar situation for walls.

In reality, the U-factor is more important, as it measures the resistance to energy of an "assembly" or "system."

 

[MiPilot]

I have 3 of HASS 700 series (R-16) doors installed or over 15 years and they have been great.

Shop is 60x64x14.
1 - 16x12 door on east wall
1 - 14x12 door on east wall
1 - 14x10 door on south wall

Our Mid-Michigan winter winds are typically from the northeast and I really appreciate the quality and insulation.