Furnace Replacement question

[gosalves]

Hi, My home is 12 years old and I am looking to save on home heating costs.

I read somewhere that an old furnace loses its efficiency and if its 10 years old, it is only 55% efficient. Is this true? My furnace is a gas furnace and is 12 years old.

1) If so, I am thinking of replacing it with a new one. What's the best one out there that is 95% efficient? How much should I expect to pay for it and also for installation?

I live in Chicago.

2) Also, is it a good idea to replace my water heaters (also gas)? Is it better to replace them (I have 2) with "tankless water heaters". Are tankless water heaters installed in the bathrooms or can they go in the basement?

3) I am thinking of adding a few more inches of insulation in the attic but concerned that too much of it may lead to condensation which could result in mold. Any ideas on this?

Thanks.

[SQLit]

There is no one that can answer your questions blind.

You have to decide the costs for yourself. The location and installation for every situation is different. Sometimes not much but enough that the safety of your home could be at stake.

http://198.147.238.24/ac_calc/default.asp What you install is directly related to how long you plan to stay and the ROI.

Insulation/weather stripping is always a good bet especially in older home. I added R-30 cellulose to my 1977 home this year in July. A/C bill was less than 1/2 in August. Not a true measure but worth the $300 bucks I paid the contractor to do the job. All of the electric bills have been down more than 40% since.

My investigation into tankless heaters proved to me that they were not for me. Check the rate of rise, then guess at what your winter incoming water temps are. That was the deal breaker for me.

[gosalves]

Thanks for your reply. The links you posted are quite useful.

My one question is:

Is it true that a forced air gas furnace loses its efficiency down to

55%, once its 10 years old?

Thanks.

[Stubby]

Not according to my plumber ad the Energy Survey I had done. 35 years old and still 83%.

[Christian Fox]

Unless the furnace has reached the end of its lifespan, it's probably going to cost you a lot more to replace it than you'll ever save by putting in a higher-efficiency model. It'd probably make more sense to wait until the furnace is closer to the end of its life (it should last at least 15 years, and possibly much longer) before you replace it.

As to the costs, the only way to find out is to get some HVAC contractors out and get estimates. There are too many variables involved to give you an accurate answer.

Tankless water heaters usually get installed in the basement and service the whole house. If you have enough demand for hot water to require two regular hot water tanks, you're not likely to be happy with a tankless model. Tankless water heaters have limits to the amount of hot water they can produce at any given time.

You can add tons of insulation to the attic, and it shouldn't cause any condensation at all as long as the insulation doesn't block the ventilation. The attic should be vented at the soffits and at the peaks, creating a draft that flows through from bottom to top.

Whether the insulation will reduce your heating costs, however, is a different story - if your house is only 12 years old, it probably has adequate insulation already.

[Pop]

HTH,

Pop

[Pop]

Many people miss the idea that insulation thickness has a point of diminishing returns. The first few inches makes an incredible difference. Succeeding inches add successively less heat loss protection per each inch. Once the optimum thickness point is reached, more insulation becomes a negligible help; other factors become more important. It's a logarithmic curve if that helps; rises fast, then slope becomes gradually less and less, approaching zero (flat) eventually. When it's REALLY cold out and touching a wall feels resonably warm, you're at or near the point of diminishing returns. Assuming proper installation, that is.

I know it varies by region, but I wonder what that optimum thickness is? Anyone know? Neglecting reflective surface, etc etc etc.. I suspect it's around 8 or 9 inches, but that's just a guess; anything over about 6" seems to make very little difference.

HTH,

Pop

[m Ransley]

I guess I hit send by mistake.

The best Kenmore gas has an energy factor of 63. Tankless go from

82-90 a certified rating to use. A Takagi or Rinnai can save you alot and at near 200,000 btu will heat all the water a household of 3 needs. I use a 120,000 Bosch and it never needs to be on high with 35F incomming water.

Get bids on 94.5% efficient furnaces.

In Chgo R 35 is code but R 60 is optimal , insulation has no effect on mold if its done right, figure what you have in inches and multiply x

3.5 per inch for an aproximate R value. 2 tanks, why, it is a waste over 1, thermal loss up the flue is the biggest thing.

[gosalves]

Thanks a bunch to all....great information.

On the issue of 2 water tanks...... is it necessary to replace them as they are 12 years old? They do a good job now, but I am a bit concerned that 12 years of sediment/build-up inside the tanks might have rendered them dangerous (just my guess since water always has sedimentation/build up)....any thoughts?

Also, to save on gas bills, I set the water temperature to 120 F (down from 140 F) on the water tanks. The water does not come out very hot now, but hot enough for our daily needs.

2 tanks for just the two of us is really not necessary. We can live with just one. The builder put 2 tanks for some reason ....may be because the previous owner had a big family and requested 2. I am the second owner.

Is it ok if I just turn the temperature all the way down on one of the tanks? Will this effectively shut it off or is it better to disconnect it physically, I mean the plumbing to and from it? Since I dont want to use one of the tanks, I dont want the pilot light to be on, wasting gas.

Thanks.

[CJT]

FWIW, unless I'm doing something wrong, that site seems to yield usage numbers more than double what I actually use.

[m Ransley]

Most 12 yr old furnaces were 80% efficient and will remain 80% if maintained. I would just turn off one tank and see if that does it ok for you Chicago water is apx 45f now , turn off the second tank and leave the first one in line to temper the water to room temp. I pulled out a 20 yr old tank in Chgo recently it had 12" of sediment, and a yellow flame it probably was down 40% in efficiency. Tankless are expensive but save the most. I would look at R 50-60 for your attic where you are. Be sure you get a written load calculation before you buy a furnace. Alot of tank loss is up the chimney, if one will do it it will be cheaper to run, I left in my tank as a tempering tank when I put in mt tankless, my savings give an apx 4 yr payback.