How long should it take to heat a house by 10 degrees?

Question

I just installed a new 80,000 BTU high efficiency furnace. Outdoor temperatures are in the mid-30s, and I'm heating a 2150 sq. ft. poorly insulated 100-year-old house. The furnace is heating the whole house fairly consistently, but when I come home from work at night, having set the heat at 60 degrees while I'm away, it takes about two or two and half hours of the furnace running constantly to lift the overall temperature of the house to 70. I only heated a small portion of the house with my previous furnace (I installed ductwork upstairs and in the back lower floor rooms along with the new furnace), so I don't have a frame of reference. Considering that I have no insulation in the walls and almost none in the attic, I'm wondering if it's to be expected that the furnace would have to work so hard to heat the place.

Answer 1

It sounds as though your heat loss is approaching
the capacity of your heating system at an OAT in
the mid-30's and a 'deta T` of 40 deg.

You should be made aware that at a lower outside
air temp., the loss will be higher and your system
may not be able to keep up with the heat lost from
the house.

An effort to cut your thermal losses, (draft reduction
at windows & doors and insulation), is something
you should accomplish before winter really sets in.

Answer 2

It has to be the lack of insulation, old windows,old doors.
- I too have a large home (2,513sq ft.). & it too is very old (110 yrs).
- We spent money & had the windows redone (12 thousand). We also had part of the house insulated. And put in 2-3 new doors.
- But the furnace is 12yrs old

It takes 15-20 mins for the house to jump 10-12 degrees. We turn the heat down to 60-62 while we sleep & when everyones at school/work.

Just because you have a NEW furnace doesn't mean you want to work it that hard. Slowly isulate or cheange doors/windows when you can afford it.

Answer 3

My house is 33 years old, good insulation, 6 year old dual pane windows and the home is 2,100 sq. ft. Also I live in Orange County CA. I had a new HVAC system put in this year. My original gas heater had 110,000 BTU's and for some reason they installed a heater with 80,000 BTU's. It took 1 hour and 20 minutes to raise the temp. 10 degrees then it shut off for 5 minutes then kicked back on for the next 30 minutes and it's still running now. My opinion is they should have installed a 110,000 BTU unit in my home so I'm not happy and they are going to hear about it! I was happy with my old heater but it was old so that's why I replaced it.

Answer 4

I think you just answered your own question. Depending on the size of the place it will take time to warm all the walls and objects especially with radiant heat which is the slowest of the heat processes. If you have any neighbors in the area, you might give one a call the night before you come out and have them turn the heat on, otherwise you'll likely want to speed heat the place some other way such as with some good quality Pelonis space heaters then let your radiant take over once up to temp.

Answer 5

It sounds like you need blown in insulation. They drill holes on the outside of your house and fill the wall cavities with blown in insulation, Heavy insulation in the attic as well proceeded by filling cracks leading to the living area with expandable foam.

Answer 6

You answered your own concern. Having a 100 yr old house with very poor or no insulation. Your situation will not get any better unless you seal cracks and insulate your house.