Options for heating/cooling Room over Garage

[Jerros]

I'm in the process of purchasing a new HVAC unit, I've had about 6 contractors come out and I've recieved a number of different opinions on what to do about the room over my garage (my master bedroom) which is constantly varies in temp by about 10 degrees. If it's hot outside it's 10 degrees hotter & humid in this room, if it's cool outside it's 10 degrees cooler.

To give a little background the home is about 1825 sq ft. It's 2 story and was built in 2001. The current HVAC system is a 3.5 ton (after a manual J I've been told that it should be 3 ton) goodman with a non-variable speed blower. The garage is finished, the ceiling above the garage is insulated (not sure how well because I can't really get a good look at it), and the garage doors are also insulated.

The room where I'm having difficulty is above the garage, it has 5 windows that face a western direction, and another 3 that face south. The ceilings are vaulted which provides less insulation room than the rest of the house. The room is roughly 16x8 and has 2 small vents.

While I realize putting in foam insulation in the garage and insulating the ceilings in the room better than what they are now might provide me better comfort in the long run, the coil in my AC freon based A/C system is dying which means the expense for a repair/replacement on this is something I can't avoid. Better Insulating the area would add an additional cost which I simply can't afford at the moment.

So onto the options the contractors have provided me.

Contractor 1:
Seems to think that a variable speed blower is going to solve the majority of the problem for me. He's going to install dampers in the trunks of the system to allow me to better control the air flow to the room I'm having problems with. He also intends to take the square part which comes out from the coil (where all the vents branch off from in the attic) and turn it into a round peice because this will get me better air flow.

Contractor 2:
Also seems to think a variable speed blower is going to solve the majority of the problem. He intends to add another vent to the 16x8 room and an extra air return in order to solve the problem.

Contractor 3:
Intends to install a variable speed blower, but thinks that Zoning is going to provide the best solution to the problem. He intends to zone the entire upstairs. (Keep in mind that the upstairs as a whole is not an issue just the room over the garage).

So I'm looking for some input on this subject. Any thoughts?

[wahoo]

I know you'll probably get even more recommendations off this board than you've already gotten from local contractors, but for my "2" cents, I'd recommend you zone the upper floor (however if you have only one unit, then the entire HVAC system must be zoned.

[the dangling wrangler]

I'll vote for #3. But, foam's the way to go.

[sktn77a]

Your problem sounds quite simple - the heat loss/gain from your master bedroom is greater than the system is supplying. You need more airflow to your MBR. If this can be achieved (eg by increasing duct size or by adding an additional duct) without compomising airflow to the rest of the house then you're in good shape. I'd have dampers and the additional duct/return installed but a heat load and airflow calculation are a MUST in this case. Zoning is another solution but this is much more expensive.

I don't think a variable speed blower will change anything unless you have it on constant low speed (even then, it won't compensate for your present 10 degree temperature difference).

[mchild]

Jerros,

A very common problem with the room over the garage is the way it was insulated. Most likely the insulation between the ceiling of the garage and the floor of the room is right up against the dry wall ceiling of the garage. If so, then there is likely a gap between the insulation and the floor of the room. This gap is likely open to the attic areas behind the knee walls which effectively makes the floor of the room uninsulated. The second issue is the insulation for the knee walls. More often than not it is no more than regular wall insulation at around R13, which is not very effective against attic heat.

Without resolving those issues the load calc is worthless as it assumes the insulation is properly installed and spec'ed.

[the dangling wrangler]

Actually, that one room could have a four ton load, by itself.

[energy_rater_La]

the bad thing about bonus rooms is that they are exposed to so much heat gain..which is why dangling wrangler says it could have a 4 ton load..(I think that is what he ment....)
think of the bonus room like this.
six sides..4 sides top and bottom.
hot air is surrounding this room.

attic temps all around.
if it is 90 degrees outside, then it is 115-120degrees in
the attic.

I had posted this link earlier, and page 5 applies to all
rooms above garages (bonus rooms) and any second story that has
walls shared with attic space.

insulation isn't enough when these rooms are surrounded by
such extreme temps. using foam/foil sheathing boards, foil tape,
button cap nails and caulk makes a world of difference in these areas. this install will also stop air infiltration and make the room
easier to cool.

I understand completly about affordability. Its enough that you have to replace the hvac system..and here I am telling you to improve your thermal barrier. But...you could add a lot of air to this room and never achieve the temp that you want due to the amount of heat/cold that transfers thru these walls shared with the attic.

In my hot humid climate we try (and try and try) to avoid west facing windows. Low e windows with vinyl frames are affordable and perform very well. In existing homes if single paned windows,
Gila makes a window tint..however tints can't be used on double paned windows. So external shading..awnings, plantation shutters
are the next step.

Its all about reflecting the heat out of the areas you are trying to cool. If you can stop the heat,before it gets into the room.... then you can cool it off.

http://www.southface.org/web/resourc...ustrations.pdf

best of luck.

[the dangling wrangler]

Exactly what I meant. It would take me an hour to type that much of a reply.

[BaldLoonie]

Mini split or small ducted system.

Friend used to live in a room above her daughter's 3 car garage. I put a 5kw air handler in the kneewall with 1 ton air handler outside. Worked great!

A mini heat pump with good cold weather heating capacity would be wise too.

I don't like zoning when 1 zone is particularly small. Too much risk of overheating or shortcycling the equipment.

[Jerros]

Thanks for all the replies. I greatly appricate all the information.


@Energy_Rater_La: Thanks I really appricate the link you posted. One of my future projects will definately be to get the garage/ceiling of the bonus room properly insulated.

[energy_rater_La]

Jerros, you're welcome! pm me if you have questions with your bonus room.

[energy_rater_La]

Oh and dangling wrangler..when I saw you were in texas..
I figured that was what you ment. I think that 4 ton load
will start in 2 months, right now its prolly only 3.5!

[the dangling wrangler]

Oh and dangling wrangler..when I saw you were in texas..
I figured that was what you ment. I think that 4 ton load
will start in 2 months, right now its prolly only 3.5!

Yes. I'm not saying it's been cold around here, just not as warm as usual. But, the humidity and heat should be back, starting today.