So what temperature should an insulated loft be?

[Ltnman]

I always thought I had a well insulated loft so it is a bit of a revelation after leaving a remote access digital thermometer in the loft, which I can read from a base station in the kitchen. Today the dawn reading is 1.5C outside but the loft is 5.3C with an upstairs room temperature around the 17.5C mark.

The thermometer has been placed on a box around 2 feet off the floor and by taking a temperature at night or at dawn I am thinking that there will be no influence of the sun heating the roof tiles.

About around two thirds of my loft has around 10” of loft insulation, the other third is boarded with insulation underneath. I have no pipes in the loft and the loft hatch is draft proofed with a small layer of insulation sitting on top of that.

I was thinking that the loft should be much closer to the outside temperature but am I thinking that loft insulation has magic properties which it hasn't.

 

[noseall]

if the movement of air is limited within any space, then the temperature will rise, particularly if that air has a certain moisture content.

a loft needs ventilation in order to balance the moisture content and prevent excessive condensation on very cold days.

 

[Alastairreid]

good answer...............think physics..............you will always have a certain amount of heat radiating from your living space.
warm air rises.. plasterboard or lathing plaster has only a certain amount of thermo dynamic qualities therefore your ambient temperature in your roofspace will always be higher than external tempreatures .

 

[Ltnman]

if the movement of air is limited within any space, then the temperature will rise, particularly if that air has a certain moisture content.

a loft needs ventilation in order to balance the moisture content and prevent excessive condensation on very cold days.

aah back to the ventilation again. You must have been peaking in my loft then???

Yes, I confess, I did have slight patches of moisture on the roof felt and yes I did have insulation which went to close too the roof line by the guttering, which I have moved back a little with a stick.

Maybe foolishly I have also cut 8 pieces of wood to open up the overlapping felt by creating one inch gaps with the pretext that it must do a little good so I can now see the roof tiles.

But despite doing all of this I had quite a temperature difference this morning so maybe I need to do more

 

[Alastairreid]

yes ok........soffit vents or tile/slate vents would suffice.

 

[big-all]

there are so many variables here

you assume the temperature out side has been that low all night it may have just dropped due to removed cloud cover/colder air from a different direction ect

there is always going to be a time lag when you have any barrier in the way
you may loose a load off heat through the roof but remember how many cubic m off heat you have to cool down

also remember as the differential reduces so does the rate of heat loss so at 5 degree difference the heat loss is slowing right down

 

[Ltnman]

Done another reading while it is still dark. It is 0.0C outside and 3.4C in the loft. As you say there are too many variables but I have found it to be an interesting excisise

 

[JohnD]

I have a feeling someone got a wireless thermometer kit for Christmas

 

[Ltnman]

Actually I have had it for a few years now. I have one thermometer in the garden and the other goes where it takes my fancy. So far its been in the fridge, porch, various rooms and now the loft.