SHOP PRODUCTS
Houzz Logo Print
sheppardk_gw

Help, buying house - furnace too small? Crazy estimates.

sheppardk
17 years ago

Long post - great drama for you HVAC geeks :) enjoy

I am trying to purchase a house. It is 2 story(1 story, plus walk out basement about 40% of basement is below grade). The house is in Reno NV in the hills at 5200 ft elevation, built in 1993. The basement was not finished when fisrt builtand the owner finished it and claims no permits were required as it had electrical and plumbing already. The city confirms there are no permits for this space. This took the square footage from 2600 to 3700. It has a 1993 (155k BTU input, "mid efficiency", "5 ton" according to one rep) furnace.

I hired a home inspector who is also a Civil/PE. He said there is "no way" the furnace is big enough. I had two HVAC reps come by and they said "way too small" "any house over 2900 sf especially if two stories needs two furnaces." One guy said the house needs 220k btu. Of course they want to sell furnaces. The house has a 5 ton AC unit and they both said that was fine as the cooling needs of the lower level are limited. They both also said the ducting on the lower level was too small and not properly installed. Even too me it looks really bad. I did my own tests and when running the furnace there is almost no perceptible air flow. The upstairs heated 5 degress(65 to 69) in 20 minutes according to the thermostat, while the downstairs did not move from 62.5 on my digital thermometer. One of the guys with the little air flow thing said it was not worth measuring. The ducts upstairs blow lots of hot air and appear properly installed. Both guys said they would need to have drywall ripped out and ceiling lowered in a the hall to properly install and permit a new system.

I am waiting on three written estimates two for forced air and one for radiant. This will only include the heating stuff. From my discussions there appear to be two solutions:

*Install second furnace* This involves adding a furnace to the crawl space, adding gas lines, electrical, venting and ducting to support it. This also requires access to all lower level ducting. The ducting is not proper and since a permit is required for the whole downstairs system the ducts must be exposed. There are not enough vents to provide proper airflow. This requires tearing out the part of the drywall installing new ducts and then replacing the drywall, texture, etc. It will also require part of the ceiling to be lowered in the hall/laundry. I will require a general contractor as this involves multiple trades and may be done after close through escrow. Potential issues/concerns with this solution:

1) The lower level will have no AC as those ducts will be connected to the new furnace, it can added later, but the lower level likely does not need AC. Another AC unit would add thousands more. The current AC is large enough, but is connected to the old furnace.

2) They may uncover other issues. One of the HVAC guys was concerned about the placement of the vents as it appeared one of the joists had been cut to place it.

3) The existing furnace is now too large so it will cycle more often making it less efficient and drafty.

The ballpark cost I got was 30k-40k!! He said this was a high estimate, but he was trying to be safe.

*Install radiant heating* This involves adding a boiler and putting an insulting layer down, then pipes for the hot water and overlayed with light weight concrete. This would also require a general contractor as all the base board needs to come off, the doors need to be cut, the closet doors need to raised. The floor level would be raised 2". New flooring on the entire lower level would need to be installed(which was planned anyway) .

Potential issues/concerns with this solution:

1) No AC downstairs if we disconnect downstairs from the ducts. Maybe they can add a damper too allow us to reconnect the ducts in summer. Considering the very light AC load this may not be a huge issue

2) The ballpark cost I got for this was ~$18-$20sf x ~1000 sf not including the work by the GC and floor coverings, base boards, etc. The cost would approach 30k

3) The existing furnace is now too large so it will cycle more often making it less efficient and drafty.

Both option would cause permits to be pulled and city inspections which could find more issues. The projects would take 3 weeks to complete if the house is vacant and they have full access.

Any comments on above are much appreciated. The seller is motivated and we want to purchase the house, but this may kill the deal.

Comments (14)