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I recently moved into a new construction home where there are rooms above the garage. I've read several articles about how you can add insulation, but I am trying to figure out what I should reasonably expect by default.

The home also has two-zone hvac where upstairs is on it's own so I am expecting better than if it was one zone for the whole house.

I used a infrared thermometer (not expensive FLIR, but basic). Taking reading from the master bedroom where the thermostat is to the bedrooms above the garage, I get typically about 7 degree Fahrenheit difference.

So Far

Test Day 1 in Sep: 74 in the room with thermostat, 67 in the rooms above garage

Test Day 2 in Oct: 69 in the room with thermostat, 62.5 in rooms above garage.

Are there any standards or code which I should be checking? I want to have the builder do at least the proper minimum before I start shelling out from spray foam or something else. This seems like something is missing for such a big difference.

Edit: I have not yet had the system blowing on full tilt for a long time for heat. Even on days when it was in the 70s outside, it would feel cold in the bedrooms, and the temp in the garage would actually be warmer. Maybe when the systems are blowing hard it will have an impact, but in the shoulder seasons when systems aren't blowing a lot I would expect closer temps across the floor in a new home.

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    How is the location of the garage relevant? Seems like the home needs a little duct tuning is all. What makes you think insulation is inadequate? Was the place built to any particular code? – isherwood Oct 10 at 20:29
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    Rooms above the garage are often colder because the garage is not heated and the door opens all the time so no thermal seal, but this seems like too big a difference. – HelpEric Oct 10 at 20:39
  • It is too big a difference for this time of year and with modern insulation practices. I'd expect at least R-25 in the floor. – isherwood Oct 10 at 21:19
  • What surfaces are the temperature taken from? Does the master bedroom have a source of heat gain like sunny windows or people? Does it have less heat loss? Less exterior wall or attic exposure as compared to the rooms above the garage? The furnace blower should mix air and equalize temperatures -- had it run much before the temperatures were measured? Have interior doors been closed and thus restricted the blower from pushing air to the cooler rooms? Insulation isn't the whole story - what about air infiltration at outlets, switches, can lights..? Check for drafts in the cold rooms. – Greg Hill Oct 10 at 21:29
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    An ir thermometer is not the best way to measure room temps. With IR you are measuring surface temps and these can be way off even in the same room. . As @isherwood said some tuning of the dampers or vents is what would be needed, you will probably have different settings for winter and summer due to the difference in heat loading and the insulation difference. – Ed Beal Oct 10 at 22:42
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Yes, there are energy efficiency code standards for residential buildings. The Code is divided into 1) one and two family structures, and 2) three or more residential structures. (There are also energy standards for manufactured housing, log homes, commercial, institutional, etc. too, but that does not apply here.)

I will reference one and two family structures only.

Each building department “adopts” their own “code”, but this is recognized throughout the U.S. This is based on the International Code Council (ICC), 2017 edition, which is the current edition.

First, you should know that the Code provides a “proscriptive path” for all building elements. If you use them, then you are approved for construction.

Second, the Code allows substitutions and “alternate means of construction “, but the calculations required to show you meet the Energy Code is difficult (and would probably require a mechanical engineer to do the trade-off calculations.) That is to say, you don’t have to use R-21 insulation in the walls, but if you don’t, you’ll need a more efficient heating/cooling system...etc.

So, here is a list (you can verify this list by calling your local jurisdiction...Building Department) and it doesn’t matter if you’re over a garage or not:

  1. Walls: R-21
  2. Flat ceilings: R-49
  3. Vaulted ceilings: R-30
  4. Under floors: R-30
  5. Windows: U-0.30
  6. Window area limitation: n/a
  7. Skylights: U-0.50
  8. Exterior doors: U-0.20
  9. Forced air duct insulation: R-8

Note: R-values are for insulation ONLY. It does not include values for siding, sheathing, etc.

  1. Gas fired furnace or boiler: 94% eff.
  2. Air source heat pump: HSPF 9.5/15.0 SEER cooling
  3. Ground source heat pump: COP 3.5 or Energy Star
  4. Ductless heat pump: HSPF 10.0 in primary space.

There are many other Energy Code requirements like : window air leakage, slab on grade performance, etc., but too numerous to list here.

SUMMARY: If your contractor met the above requirements, I’d expect better performance in your living space above the garage.

If the space is not too cold (in heating season) or not too hot (in cooling season), then the heating system is of adequate size.

I’d then check thermostat. Some have a “dead zone” setting...usually about 3 degrees. That is to say, if you set it at 70, then it must drop (or rise) 3 degrees before it turns the heating/cooling system on. If the thermostat is located in a drafty area (say by an exterior door) it could trigger the thermostat.

I would then check insulation thicknesses. One easy check is to see if the walls are made out of 2x4’s. The required insulation cannot be installed in 2x4 walls...a 2x6 wall is minimum. (You can easily check thickness of walls by looking at the walls by the windows.)

I’d check the ceiling insulation, because heat rises and you’ll quickly loose heat through the ceiling/roof quicker than walls. (Likewise, If cooling is an issue, then check the floor insulation. )

If the windows are not double pane or the exterior door does not have weatherstripping, then they do not meet minimum requirements.

Remember, your large temperature change is caused by a lack of retaining your heating/cooling AND your heating/cooling system not responding quick enough.

  • Is there any way to validate or determine the R-values other then asking the builder what was used and where it was used? I agree there is probably a lack of insulation above as well as below. The way the two rooms above the garage are setup, they each have 2 walls exposed as well. If the wall are 2x4 then how would you ever fix this? – HelpEric Oct 10 at 23:24
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    @HelpEric You need to become a detective and mechanical engineer. Remove electrical outlet covers and measure thickness of wall, (with a non-conductive device...like a plastic comb.) R values are determined by material and thickness. That is to say, 6” fiberglass insulation will equal R-19 or R-21, depending on density, etc. If you post the thickness of the insulation with picture then someone can tell you what the R-value is. BTW, garages are typically built with 2x4 construction. Hopefully, the contractor changed to 2x6’s on the upper living space rooms. – Lee Sam Oct 10 at 23:47
  • I measured and it looks like these are 2x4s for the walls based on how far I can get in and then measuring in the window well. I could get a good look around the outlets without cutting, but around the vent I did see some bat insulation there. The ceiling had recessed lights, when I went up there I could figure out how to take the inner covering out and look around, but it wasn't overly drafty. What's the solution here, ask for spray foam? Is there a specific line item in code I can quote here? – HelpEric Oct 11 at 20:05
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    @HelpEric The 13+5 is in reference to rigid insulation added to the exterior side of a 2x4 wall. The 2x4 wall with batt insulation equals R-13. Often we’ll retrofit exterior walls by removing the exterior siding (and moisture barrier) , then installing a rigid closed cell insulation board with an R-value of 5, and with wood stripping at 16” or 24” on center to match the existing stud pattern, then reinstall moisture barrier and siding. (We use the stripping to nail siding into.) I doubt the rigid board was originally installed because it’s expensive and switching to 2x6’s is cheaper. – Lee Sam Oct 12 at 15:32
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    If you’re looking for a lever to use on your contractor, I’d ask him what proscriptive path he used for the 4” stud walls. I’d talk to the Building Department and ask them why they allowed this? – Lee Sam Oct 12 at 15:38

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