Insulation Performance Overnight

Aeneas

Temperature outside last night fell to 4 degrees. Temperature in my living room fell from 20/21 around 10pm last night when heating went off to 15 degrees at 8:00am this morning when it came back on. Would a drop of 5degrees overnight be regarded as adequate insulation performance?

bauderline

Tis like asking how long is a bit of rope ?

How old is your house, what type of construction is it, what type of windows do you have ? Are you in an exposed area ?

Was the door to the room left open ? ... That is not as silly as it sounds, I close all the doors to my rooms at night firsrtly for heat retention and draft reduction and also it supposed to slow down the spread of a fire.... useful exercise.

I would say that given the cold night that was in it and past irish building standards it is not that surprising and would reckon it is all too common. It is not too good though, I would expect a modern well insulated home to hold the heat much much longer....

b.

Aeneas

Thanks. I thought about the "how long is a piece of string" question when I made the post. There are so many variables. But your answer is interesting. In the "modern well insulated house" you mention have you any idea of an acceptable temperature drop in the conditions I outlined? Mine was five degrees from 20 to 15. What would be acceptable --17 -18 over ten hours?

Reyman

Sound fine to me. 5 degrees would be pretty good overnight. But then mine is a pretty old house with 9" concrete block walls and if you have a new house meeting the latest insulation standards it should be better.

10-10-20

Don't forget that a house/room with no contents will cool quicker as there is less mass to retain heat! The walls also collect heat and radiate it slowly if they are insulated correctly.

My house will frequently drop from 21 C down to 15 or 16 overnight, but with a wind the rate of loss is faster.

If in doubt, check the insulation in the attic space. Guidance these days is anything up to 300mm of rockwool.

Aeneas

I have 300mm fibreglass in the attic and warmfill silver beads in the cavity. The room is a single storey extension with three external walls and a fair amount of glass. A lot of discussion about insulation is about R and U-values and insulation types and thicknesses, and building standards. All necessary and important. But I thought I would do a practical test. My main interest is in knowing whether a 5 or 6 degree fall in temperature (from 20/21 to 15) over 10 hours overnight, when temp outside is three or four degrees, is reasonable/acceptable by current standards.

10-10-20

OK, my house isn't as well insulated (but improving) and last night it dropped down to 13 degrees downstairs.

ttm

If you want another interesting comparison with a really old house with NO central heating no dpc and no insulation....

Stone built cottage 60cm thick stone and mud walls with cement render inside and out, in cold spot with very little winter sun. Tin roof over remains of old thatch.

Only main room heated with woodburner. Nightime with woodburner (approx 8kw max output) 20+ C, morning and during day with no heat so far this year not below 15 C. Thats probably because the wood burner pumps heat into a massive unlined chimney which holds a lot of heat.

Aeneas

That looks pretty good for a house that does not have modern insulation. In my own house the warmest room is also one without modern insulation - mass concrete walls from the 1950s, but the walls are lined with books, which presumably hold in the heat. I'd still be interested to know whether the insulation performance for my living room described above is adequate. Does anyone know of any ready way of measuring/calculating this?

ttm

I think its the books that keep it warm

Go into so many houses and no matter how well insulated or well heated they are you won't find a book anywhere - the house feels cold

Plenty of books in our house too

There is a calculation you can do to find out how good your insulation is because if you can measure how much heat you are using to maintain a steady internal temperature and know the external temperature then the linking factor has to be the rate of heat loss which is related to the U value of the insulation. Problem is of course working out exactly how much heat you are using, easy if you are using electic heating not so easy to work out if you are burning wood.

These couple of websites give you some idea however they do the std calulation to work out how much heat you'll need so you can get the right size boiler but we need to change it round so we can work out the U values.

http://www.diydata.com/planning/ch_design/example1_imperial.php

http://www.plumbingpages.com/featurepages/Heatloss.cfm

Should be something like ....

U value = Room Surface Area x Temperature difference / Heat Loss

Any heat we are putting in is the Heat loss?

Anyone up for a better explanation?