Ideas wanted for a very cold house extension.

Dave7

Legendary Member
Location
Cheshire
Situation is.......
30 years ago we had a full "granny flat" built for MrsDs mum.
Its single story.....east facing but not exposed.
Lounge, bedroom, bathroom, kitchen.
It has always been difficult to heat.
We know the walls were insulated.
Later I paid for extra roof insulation.
C/h rads are original, boiler is quite new.
Never been a big issue BUT......daughter and SiL may be buying the house and we would move into the flat.....so we want it right.
Bigger boiler ??
Bigger, better rads ??
Under floor heating (no idea how that works with concrete floors ??
More insulation pumped into the walls ??
All the above ??
Any thoughts ??
 

bikingdad90

Veteran
I’d go for cavity wall Insulation, at least 400mm of insulation in the roof, and if there any big french doors, Maybe take one out and replace with a window to minimise heat loss and then look to upgrade it all to triple glazing as double glazing losses efficiency overtime. Don’t bother with electric underfloor heating it is too expensive.

As you have concrete floors, another heat loss source, consider insulation underneath the underlay and carpets.
 

T4tomo

Guru
30 year old, radiators wont be anything like as good as modern "double" ones at throwing out heat. also is it on same CH as rest of house? If so it could be at the end of the run, so the main house rads are taking more of the heat, you maybe able to compensate by balancing the rads a bit, but would be better on its own circuit with a separate thermostat.

I guess it will come down to insulation, single story is less efficient to keep warm, unless it has top notch insulation
 

midlife

Guru
Aside from the cold I guess you have been into the "deliberate depravation" side of selling to your family.
 
OP
Dave7

Dave7

Legendary Member
Location
Cheshire
30 year old, radiators wont be anything like as good as modern "double" ones at throwing out heat. also is it on same CH as rest of house? If so it could be at the end of the run, so the main house rads are taking more of the heat, you maybe able to compensate by balancing the rads a bit, but would be better on its own circuit with a separate thermostat.

I guess it will come down to insulation, single story is less efficient to keep warm, unless it has top notch insulation
Thanks.
The extension is on its own system eg its own boiler (and thermostat) which is only a few years old.
Insulation seems a good way to go.
 
OP
Dave7

Dave7

Legendary Member
Location
Cheshire
I’d go for cavity wall Insulation, at least 400mm of insulation in the roof, and if there any big french doors, Maybe take one out and replace with a window to minimise heat loss and then look to upgrade it all to triple glazing as double glazing losses efficiency overtime. Don’t bother with electric underfloor heating it is too expensive.

As you have concrete floors, another heat loss source, consider insulation underneath the underlay and carpets.
Some good points there .
It does have big sliding doors......maybe modernise to triple.
Re the underfloor heating...... a CC member (who has sadly disappeared) swears by it. Why do you say its expensive ?
 

bikingdad90

Veteran
Electric underfloor heating works like an induction hob, the electrical current heats the coil which in turn heats the concrete and flooring, no electric current and everything starts to cool quickly. We had it in our kitchen, few hours on a morning and a few hours on an evening over winter and the bill for that bit alone was near to £500!
Proper underfloor heating with water pipes is much more efficient as the heat radiation comes through after it’s off so the concrete and floor takes longer to cool and reheat each day.
 

figbat

Slippery scientist
With u/floor heating you need to make sure the floor is insulated beneath the heating, otherwise you are paying to heat up the Earth. With an old concrete floor this means either adding a layer of insulation then flooring on top, or chasing the heating elements into the concrete. The first option raises the floor a lot. The second is a lot of effort. We looked into this when we renovated our house but in the end went with a couple of large, vertical radiators.
 

HMS_Dave

Grand Old Lady
Location
Midlands
I hear the MOD will have some spare Nuclear Reactors from the old Trafalgar Class submarines once they are all decommissioned. You'll be talk of the street!
 
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