My single-family colonial has a large (24x24) Family Room over the Garage. The temperature of the room is noticeably different from the rest of the house, by approximately 5-7 degrees on average (summer and winter). There are quite a few angles I can approach this from, but I can't afford to do everything at once and need to approach in stages that will make the most notable impacts possible.

I've had 3 insulation professionals out, whom all provided different suggestions on where to start, so I figure why not a few more? Options discussed to date:

Insulate ductwork - the main trunk (and return) for my oil/forced air system runs 50+ feet, with many branches along the way, then through the garage ceiling before finally releasing into the Family Room. It is sealed with duct butter, but otherwise uninsulated. It leaks a noticeable amount of air, as the basement is quite cold in the summer and hot in the winter.

Replace Garage doors - 25 year old, wooden, uninsulated doors (though I did seal the perimeters with weatherstripping last year).

Further insulate Garage ceiling - the Family Room floors are quite cold in the winter and the ceiling contains the forced air branches for the Family Room.

Further insulate cathedral ceiling - snow melt was almost non-existent over the winter and thermal camera looked quite good, but this is always an envelope consideration.

Further insulate perimeter walls - thermal camera test wasn't as good as the ceiling, but not terrible.

Install ceiling fan - may help, if it is a distribution issue

Any and all thoughts welcome. Thanks in advance.

There are two main objectives here: insulation values and air leakage (infiltration). Both are important in heating, but the air leakage has been pretty much ignored by builders up to now, and is likely why the floor "feels cold". So the garage needs to be airtight from the family room to start and the garage ceiling should end up as close to R-60 as you can make it. The heating ductwork should be well sealed and be INSIDE the insulation.

I'd think in terms of two projects - a) getting the room comfortable and b) saving money. Some overlap, but mostly separate issues.

Sealing the ducts is likely to be an easy boost for both. Then you can look at things like adjusting duct flows with dampers or booster fans and adding some electric heat or a mini-split (which compares well to oil).

For b), look at the entire house (consider an energy audit) and insulate/seal wherever you see the best ROI. Don't put R60 in the family room while you have R15 elsewhere.

It is hard to give advice from afar without all the information.
First, bonus rooms over the garage often have very high heat loss because they have unconditioned space on 5 of the 6 sides. There is just a lot of surface area. Secondly cathedral ceilings are often poorly insulated. From a practical point of view, there is not enough heat provided by the forced air system to heat/cool it. It may be that the system is leaking air, or the air is cooling too much on the way to the garage, or it may just be undersized for the heat loss. In the end you need to supply more heating and cooling, or reduce the load. Deciding which approach is better is the hard part. If you ask an insulator- they will tell you insulation, if you ask a HVAC contractor they will give you a HVAC solution.
As an energy auditor, I would want to start with some duct diagnostics, and then move onto the shell.
Measure the total duct system airflow. Measure the static pressure drop across the filter, A coil and the whole heater . Measure the total duct leakage. If you can measure duct leakage to the outside of the house (this is done by combining the duct leakage measurement device(called a Duct Blaster) in conjunction with a blower door.
Measure the temperature and air flow of the return air, and supply air in the main trunk, same with the registers into the garage.
Now you can understand the system performance, and figure out how much losses there are in the heating system between combustion and delivery. You also know how many btu’s of heating or cooling you are delivering to the room. Now you can make good choices about how to make the system perform better.
This is the first piece of the puzzle
The second is the shell. An accurate assessment of the current insulation on all sides of the room, as well as some information about the infiltration rate, then calculate the total heat loss of the bonus room, using Manual J8 will help you decide what the most effective way forward is.
In short you need a good evaluation, and a plan for moving forward. Then you decide what to do next. The next steps may depend on whether you are just interested in a comfort improvement, or you are interested in comfort plus energy efficiency. Each may have different cost effective solutions.
Without actually testing, you are just throwing darts at the problem, hoping something sticks.

Good Luck, and if you can get someone to give you the numbers I outlined above, we can be of more help.
Cheers, Eric

I'll second Eric's suggestions. You need some firm numbers and guidance before hiring anyone; preferably from someone who visits your home and is only "selling" knowledge. As far as the insulation levels, the rest of your home is presumably above a 50-60o basement, while the family room is above ambient exterior temperatures. (Any heat currently in the garage is probably leakage from the house.) The vast majority of "bonus rooms" I've seen are not air sealed from the cold garage underneath, and are poorly insulated with fiberglass batts, so the temperature differential you are seeing is normal and a result of this. The remedy is to air seal the ceiling and insulate to the necessary degree. Air sealing is a new specialty and must be verified with a blower door test, so it may take some looking to find the right contractor.

Typically above garages the floor bays are open at either end. We seal each bay and dense pack.
The kneewalls are typically just batts open to knee wall attic, we correct fiberglass, seal penetrations and install sealed foam board over knee walls.
Duct work is often in the knee wall attic space or along the roof ridge attic space. We insulate ducts if we can, box them in with foam board with possible and install supplemental electric baseboard if we can.
Sometimes in truss construction the gable wall is drywalled over the truss, what this means is you have 1.5" of insulation if any at all. Then we build a new interior gable wall.
I see alot of weird framing errors in these spaces, I believe because of the basic angle cuts and total lack of decent carpenters.
I guess if you really needed the room, tearing out the drywall and starting over makes the most sense.

Its about the best you can do with one of the dumbest cold climate living spaces made.

Posted By greentree on 24 Aug 2014 12:54 PM

Its about the best you can do with one of the dumbest cold climate living spaces made.

That sums it up. Living spaces above a garage are a detailing nightmare and pose a threat to your family's well being. 90% of the time contractors butcher the details of these spaces and you end up with hot/cold rooms, mold, air quality issues, and a host of other problems. Many documented cases of where Carbon Monoxide has found its way into the living space and caused poisoning and/or death. So air sealing of the home from the garage is a top priority. The one episode of Holmes on Homes showed that an HVAC duct was somehow disconnected and bringing CO air from the garage into the baby's room of the home. Luckily it was caught in time.

In my area they require the garage space to have 100% open 24/7/365 outside wall air vents to the garage. While this makes the garage basically open to the outdoor air temps it brings in fresh air and helps removes the CO (as long as the car is off). I would check with your local building dept to see what they require when you put a living space above a garage area.

Further sealing the garage area space and making it airtight can backfire on you because all you are doing is trapping deadly CO gas in the garage. Don't treat the garage space as living space, treat the garage space like outdoor space but treat the living space above the garage as trying to keep the outdoors/garage space out.

I would also consider using two layers of Type X 5/8" drywall on the ceiling area in case of a car garage fire.