Heated Garage

[Energystar]

I am building a home with a heated garage. The garage is insulated well below prescriptive code requirements and of course the garage door cannot meet fenestration requirements. However, the customer wants to install a PTAC unit in the garage to make it more comfortable, but not to the temperatures required for conditioned space. The plan reviewer says that the installation of the PTAC would violate the following section of the code because it would be considered “conditioned space”.


The IRC defines conditioned space as follows:



I would argue that the garage is certainly not within the “building thermal envelope” and is therefore not “conditioned space”.


As you can see, the two definitions rely on each other. I’m pretty sure I got scolded for that in English class at one time or another.

Another strange issue is that as written N1102.1 only applies to homes using the Prescriptive Compliance Option. Even though I am using the Performance Compliance Option, the official still insists it is in violation.

I find it hard to believe that this is the intent of the code.

 

[Msradell]

Unfortunately, I can see where the planes reviewers coming from. By adding the PTAC he sees that you are turning the garage into a "conditioned space" with you in reality you really are. Even though it won't be taken to the temperatures of the interior of the home it will be conditioned in relation to the outside. I'm afraid it's going to be an uphill battle to convince him otherwise.

 

[Keystone]

Try and speak to his boss.

Maybe the plan reviewer is under a tight leash, maybe the plan reviewer is thinking they are righteous and saving the world but IMO if someone wants to spend money and heat a garage every so often then so be it.

This is no different then a heated pool, provide a cover. Okay great we all know that cover is moved pool to pool. Stop the absurdity. Your gaining superficial compliance which is worst because it gives less credence when a code truly must be enforced.

 

[e hilton]

Install an electrical outlet in the garage for “future tool TBD” and tell the owner to install the ptac next year.

 

[Sifu]

Using '21 IECC R502, it requires full compliance with the code. So, fully comply with R402.2.12 which has lower required R-values for heated garages, maybe that helps. Then fully comply with R402.3.5 which allows for lower fenestration requirements, maybe that helps. I thought there was something for the slab on grade insulation but I can't find it. Maybe someone else knows where it is or where it went. Worst case, add some external slab insulation if that exception can't be found, unless you are in zones 0,1,2,3 or are in a heavy termite zone. Maybe it is easier to add blown insulation in the attic for some trade-offs? Maybe a REScheck can help.

Code is what it is, take advantage of it as best you can. Or use really inefficient space heaters and use more energy....forced non-compliance at it's finest.

 

[klarenbeek]

1102.2.12 allows for lower insulation values for heated garages if separated from conditioned space (the house). Table 1102.4.1.1 requires air sealing between garages and conditioned space. ACCA Manual J also requires separation between garages and conditioned space. The heating and cooling load calcs in Manual J are for occupied space, not the garage so there is not required minimum/maximum temp you have to maintain. Because of this, you can size the equipment in the garage to meet whatever setpoint you pick.

In my mind, all of these imply that conditioned space is intended to mean the dwelling unit.

As a last resort I would take e hilton's advice and just put in an outlet for future use.

 

[steveray]

Agree with Sifu.....once you condition it, it is conditioned....and has to comply with the envelope or low energy

 

[Energystar]

Thank you all for your excellent advise. I had already contemplated e hilton's method, but I still need to frame an opening for the PTAC, trim around it, etc. We are in CZ-4, 2018 code. I think sifu and klarenbeek's solution should work. I have successfully used future code versions before to justify things and I think it will work here. Below is the verbiage from the 2021. They added heated garage to sunrooms.


These are the exact insulation amounts we planned to use and the wall between the home and garage is totally compliant and airtight. The other curious part of this code that I don't understand is that these sections only apply to the Prescriptive Method even in the 2021 as is stated in the following section. I must assume this is an oversight by the ICC:


I wanted to add that I am just a builder, but as such I would call myself a student of the code. I don't post much here, but I very much enjoy reading the posts and have learned a lot from these discussions from some obviously very knowledgeable contributors. Keep up the good work!

 

[Sifu]

I wanted to add that I am just a builder, but as such I would call myself a student of the code. I don't post much here, but I very much enjoy reading the posts and have learned a lot from these discussions from some obviously very knowledgeable contributors. Keep up the good work!

"Just a builder"? If it weren't for you we might all work at wal-mart (some days I would prefer that). Man of us were/are builders and sometimes still "students of the code". Please feel free to come back and contribute to the conversations. Let us know how it turns out.

 

[klarenbeek]

I agree with Sifu. Like I tell friends both from my days in the trades and ones I've made since becoming an inspector (yes, it happens!), they're the ones doing all the work, I just walk around and look at it all day

 

[ICE]

The garage is insulated well below prescriptive code requirements and of course the garage door cannot meet fenestration requirements.

Seems odd that the question would be asked.