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I recently insulated my flat roof with blown cellulose insulation. I installed two vents on the roof as well. The house used to warm up well at 72°F. In order for our bedroom to be warm we have to set it at 74°F. I don't understand how after we insulated the whole house from the roof that we have to increase the temperature on the thermostat two degrees. Our bedroom which is the coldest is furthest from the furnace. But prior to insulating it is was fine at 72°F.

Why would this be, and how can we fix it?

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Is this a one storey or two storey building? Where are the bedrooms? –  bib Dec 22 '13 at 17:40
    
This is a two story house, there are 3 bedrooms in the house. Two are in the rear and one in the front. –  Tariq Dec 22 '13 at 18:33
    
Are the bedrooms on the ground floor or upstairs? Where is hte thermostat? –  bib Dec 22 '13 at 19:06
    
Bedrooms are on the second floor, thermostat is in the hallway of second floor. The bedroom is 4 degrees colder than the thermostat reading. –  Tariq Dec 22 '13 at 20:14
    
Do any heating ducts run above the insulation? –  bcworkz Dec 22 '13 at 20:34
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1 Answer

You say “thermostat is in the hallway of second floor”

The hallway used to lose a lot of heat through its ceiling; it does not do so any more, so for a given temperature, it needs a lot less input of heat.

A bedroom also looses less heat through its ceiling then it did before, however it still loses heat through its outside walls. So for a given temperature it needs a little less input of heat.

The thermostat is reducing the input of heat based on the needs of the hallway; the hallways needs have reduced more than the rest of the house.

So you need to turn down water flow to the radiator in the hallway, so it takes longer to heat up. (If you have a hot air system you need to block up its outlet into the hallway.)

This is why it is best to put radiators under windows on outside walls, so the parts of the building with the most heat loss gets the most heat input.

The normal setup in the UK, is to set the thermostat higher then you want, then control each room using TRVs. There are better setups but they cost a lot more.

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Thanks for the great input, I don't have a radiator in the hallway where the thermostat is. It's in the hall en route to the two bedrooms on the second floor. I have a two zone system. –  Tariq Dec 23 '13 at 19:15
    
@Tariq, heat rises I expect you have a radator somewhere below were the thermostat is. –  Walker Dec 23 '13 at 19:28
    
There's a radiator prior to coming up the stairs in the hallway on the first floor. It's a weird setup in this house. One radiator is along side an interior wall and not under the window of my sons room. How bout adding another radiator in our bedroom, I have two exterior walls and only one radiator. –  Tariq Dec 23 '13 at 20:40
    
How about using a sensor in the bedroom for the thermostat? –  Tariq Dec 23 '13 at 20:41
    
You may do well to re-balance the system so more heat comes out of the perimeter radiators, the bedroom in particular, and less out of interior radiators such as the one close to the thermostat. Depending on the exact nature of your system, there is a different way to accomplish this. –  bcworkz Dec 24 '13 at 2:10
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