Gas and Oil Home Heating Furnaces - System unbelievably inefficient

Purchased 5-year old home, 3600 sq. ft., in Dallas and got a really ugly surprise during the summer - $600 electric bills and a hot house. Neighbors bills are less than half of that and nice and comfy.

I have 2 zones, both units located in the attic. Each unit only has one return, both are located in the common area of the house. In addition, the unit that primarily services the master bedroom also provides service to the common areas (this makes no sense to me...help?). There are several rooms that get very hot (main thermostat is in one), and we have ceiling fans all over the place.

I've had some HVAC guys out and they concluded that there are several minor issues with the systems, but I have enough tonnage to cool the house. After some head-scratching they recommend an analysis of the airflow through the vents ($300).

I did a little research (this is my very first experience with this stuff) and learned that there are some things I can do myself that could greatly improve the efficiency of the system, mostly regarding the duct system. Sealing joints and that sort of thing.

My main question (although ANY suggestions will be gratefully accepted) gets back to the ducts - shouldn't the units be pulling air from each room instead of just one pace each? Would reworking the ductwork and making it as efficient as possible (and what exactly are the details around THAT?) help me out?

Also look at: insulation completness and effectiveness, air leakage, and where the sun shines on the house - windows and such for heat load, attic ventilation and heat load on the ceiling. I think central returns to the HVAC limit its effectiveness.

There are many things to consider.

Having the ductwork sealed on my 65 year old house made a lot of difference.

Hope this helps.

Id go over the whole duct work and see what you have there in size. Like here ,I have found that they dont cut out all the return air in the drywall behind the grills sometimes. Say like for 3 ton I like 240sq" one home I had here only had 144sq" back to the unit for the cold air return .The same holds for the out let duct.
Some of the old tape could come off the duct. Have better tape now.
Most of our jobs have only one return now. If you set the door jams up so you dont have to cut the door off and you use the right registers for the throw and spread of the rooms it works.

One home in Missouri that I have kept tabs on . 3 units for 6 ton AC & Heatpump. Cook, 2 hot water tanks, water pump lots of light and 3 kids 4600sq ft $150.00 per month for the year

Like chfite said good vents in the attic, Insulation? The neighbors home
Same builder?? Same hvac company?? Is their duct lay out about the same as yours?;) ED

$600 is unreasonably high. Have you had TU check the meter to make sure it's accurate and no electrical problems? It's also possible that they estimated your bill for a month or two and had to play catch up - they should be able to tell you that if you call them. It wasn't that hot this year. You don't have an old refrigerator or freezer running in the garage do you? Unusual amount of dryer usage? Windows open??

Otherwise, I think you probably need some insulation in the attic. Solar screens or film help too if you don't already have them - when I added them, my bill didn't go way down, but my comfort went way up. Before I spent any more on air flow analysis, I'd blow $200 worth of Cellulose into the attic and spend $100 on calking and see what problems remain.

With 4 people living in our 3100 SF 5 y/o house, my highest electric bill this summer was just over $200 and we were quite comfortable.

Good luck. How well does the house heat? Should find out tonight...

Doug M.

Excellent - thank you all very much. Sealing the ducts and adding some insulation wouldn't hurt, no matter what.

Ed - the contractor I had out mantioned he wasn't sure about the size of the ducts...How should that be measured? duct area? cubic ft/min? Is there a way I can figure out what it should be? Or is bigger better?

Doug - the house heats better than it cools, but that's still not very well. Excellent idea about TXU, I'll call them.

What do you guys think about cutting a small return in each room and feeding it into the main return? That should at least turn the air over more often in each room, particularly in the hot ones. Worth the trouble or will that mess it up worse?

Remember, every hole made and pipe added is another potential leak in the hot attic and source for condensation. If you add returns, make sure to insulate them well so they don't sweat. Adding a few low to the floor might help the house feel warmer in heating season too. I wouldn't make any air adjustments before the insulating is done.

Doug M.

I've been crawling around in my attic into some of the less accessible areas to determine how much insulation I have in place. Most had between 9 and 12 inches of blown fiberglass on the attic floor and batting on the walls between the studs.

Surprise number one: some of the batting has fallen from between the studs and is just laying on the floor. Bare sheetrock between me and the attic.

Surprise number two: One area about 10 ft by 5 ft on the attic floor had no insulation whatever on the floor.

Clearly, this is really bad, but it's pretty easy to fix. My question is if anyone would make an informed estimate on how much inefficiency can be attributed to the lack of insulation, especially the one on the attic floor.

I'd also appreciate any opinions on if adding a radiant barrier system would be worth the money. I realize this isn't really HVAC-oriented anymore, I'm grateful for your patience...

Try and go to this www.ornl.gov/sci/roof+walls/radiant/rb_tables

I think will tell you what you want to know about insulation. They also say its not worth it for R/B in the long run. I also cant see its worth it just dust cuts it down.I think more you should think about the attic vents and do you have enough for summer or winter. You didnt say what you had for vents??????? Also some times they can cheat on that blown F/G insulation. They just open up the air shutter more and you get the 12" but not the insulation as should be there or what you paid for

$600 for the summer lets look at the vents here for sure;) ED

We just had our roof re-shingled and replaced 4 passive vents with wind turbines. There are about 8 additional passive vents in addition to the new turbines. This particular house has no soffits vents at all.

The attic never got that hot, but maybe that's 'cause it was making the house hot first...

I have "cool deck" which provides a radiant barrier and I agree that it will probably take the life of the mortgage to see any return on it. I don't have any numbers on the savings that proper insulation will bring, but I know it makes a drastic difference in the way the house feels. I've added insulation to several houses as well as made other improvements like calking, new ductwork, storm windows, and solar screens. The insulation has always made the most noticeable difference. The only improvement that's even come close to being as noticeable is the addition of solar screens.

Doug M.