Notice what seemed to be a strange thing on our deck out the back.
Snow was clearing from between the gaps in the decking, and melting over
the screw heads even though it was sub-zero.

What I think is happening.
When the extension was built, ventilation channels from the suspended
wooden floors (original) were installed in the solid floor to allow
underfloor ventilation to avoid damp.
The underfloor area is above freezing.
Air is flowing under the house and warming a bit, then flowing out under
the deck at the back.
Sort of very minimal under deck heating.

Until I saw the snow and ice melting I had never considered that there
would be any real heat loss through the under floor vents.

Then again you wouldn't want the under floor area to go sub-zero.

The most of the joists are insulated to keep the ground floor rooms warm.
Perhaps I should revisit the amount of lagging on the underfloor pipework.

Cheers



Dave R



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On 9 Feb 2021 11:46:47 GMT, David wrote:

Notice what seemed to be a strange thing on our deck out the back.
Snow was clearing from between the gaps in the decking, and melting over
the screw heads even though it was sub-zero.

What I think is happening.
When the extension was built, ventilation channels from the suspended
wooden floors (original) were installed in the solid floor to allow
underfloor ventilation to avoid damp.
The underfloor area is above freezing.
Air is flowing under the house and warming a bit, then flowing out under
the deck at the back.
Sort of very minimal under deck heating.

Until I saw the snow and ice melting I had never considered that there
would be any real heat loss through the under floor vents.

Then again you wouldn't want the under floor area to go sub-zero.

The most of the joists are insulated to keep the ground floor rooms warm.
Perhaps I should revisit the amount of lagging on the underfloor pipework.

Lagging the pipes is well worth the effort - much less trouble than trying
to repair a pipe.
Had this with a house - the front rads. were fed by pipes that ran inches
from an air brick in the NE wall. Ventilation very necessary, couldn't get
my 6' 4" ubder there, no easily kidnappable small children etc. but managed
to slide insulation all the way along.
It'll always be a bit warmer than freezing weather under there as heat comes
up from the ground. I've seen water trickling from under a bank of snow in
-5C weather - the road was a mess!
At -2C this morning the slabs on the path were free from the light snow as
they still have a bit of heat under them (well, a lot but most isn't of
use).


--
Peter.
The gods will stay away
whilst religions hold sway