Klaus Kragelund wrote:
Hi

I have a basement in my house. The floor is about 1.5m below
earth/ground level and it is concrete about 30cm thick

The floor is not insolated, so in order to save some money on the
heating bill I am considering insolating it with sheets of polystyrene
foam (in principle foam filled with air) with some rafters in a mesh
to

lay the wooden floor on. The lastly add 20mm of wooden plates/floor

An architect has told me to break up the floor and lay a new one with
30cm of extra insolation

But, I wonder if any of you guys can help me. I am an electrical
engineer and I don't like to do this without calculating the needed
insolation instead.

My theory is that since the floor is 1.5m below ground level, the
temperature of the soil will never be very cold. Searching the net I
find something about 14degree celcius.

So if I have 60square meters of floor heated to room temperature of
20degrees, how do I calculate the heattransfer when I have the data
for

the insulation and the concrete floor?

Will the earth behave as an ideal giant block that has 6degrees of
tempeature. So the gradient from the room temperature to the earth can
never be higher than 10 degrees (20-14)?

Numbers:

Concrete, k = ~1W/mK
Polystyrene, k = 0.03W/mK
Wood, k = 0.14W/mK

Power needed to keep temperature stable: P=KAT/D

Concrete using 60square meters and 30cm thick: P = 1*60*6/0.3. P =
1.2kW

Adding polystyrene: k = 0.042 , P = 0.03*60*6/0.05 = 216W

The poystyrene is in parallel with the rafters. Assuming the rafters
take up 5% of the floor instead of the polystyrene

P= 0.14*60*0.05*6/0.05 = 50W

So from these calculations it seems I need 250W to keep the room
heated

(not counting the walls)

Any wrong doings in the calculations - comments?

Thanks

Klaus Kragelund

Well, 1.5 meters is about the break even point for your question. So I
would suggest worrying about the wall, but not the floor. However if you
have long cold winters or long hot summers, then you might want to also work
on the floor.

--
Joseph Meehan

Dia duit