single room UFH kit for extension, existing boiler capacity Question

[boss_cat2]

Hi all, new to this site so thanks in advance if anyone can help us.

We are looking to build a 2.8 x 4m extension onto our house, we will remove a wall and enlarge kitchen dining room but we will have limited wall space hence the first thought of an under floor solution.. For the new extension building warrant drgs show concrete with 90mm insulation and 75 mm screed for a “ wet” underfloor heating system kit. However we seek advice on whether our existing Baxi 105 e combi boiler, which is a 31 kw system, and heats all radiators in 4 bedroomed house will cope with the additional work load, note the two small 50 and 80 cm radiators will be removed, (see below). I believe this UFHS can be done by adding a manifold second timer and pump system single room kit!!

We live in Scotland, 100 year old house and solid walls, we have insulation in roof and old sash and case windows.

WRT to radiators, we have
Kitchen 1 x 50 cm D
Dining room 1 x 80cm D
Hall 2 rads – 1 x 140cm S; 1 x 100 S
back room 1 x 100cm D
Living room 1 x 100cm D

Bedroom 1 - 1 x 107cm D
Bedroom 2 - 1 x 107cm D
Bedroom 3 - 1 x 100cm D
Bedroom 4 - 1 x 87 cm S
Towel rail in bathroom

Gas usage in summer low but in winter it is 1 to 1.5 therms and in winter 3 to 3.5.

We went for UFH as limited wall space for radiators. I also was going to add two plinth heaters under future kitchen units in the existing dining room which will become the kitchen, again due to limited wall space. This was to be supplemnted with wire electical mats, under tiles and only for am when waling on bare feet for the 1 hour or so when we getb up. ( note we also have solar PV 4kw system on roof.

We are looking for any advice on whether we can use existing boiler, and perhaps to get a rough cost estimate for this , I see a kit is approx £400.

it may be that we have to go for something else entirely, for example one builder mentioned carbon film and chanag

b tiles to laminate.

Thanks in advance

 

[doitmyself]

we seek advice on whether our existing Baxi 105 e combi boiler, which is a 31 kw system, and heats all radiators in 4 bedroomed house will cope with the additional work load. We live in Scotland, 100 year old house and solid walls, we have insulation in roof and old sash and case windows.

31 kW is probably OK. But, to be on the safe side, use the Whole House Boiler Size Calculator using your current house dimensions, then add in the known heating requirement for the new extension. You should set the Hot Water allowance to 0 kW (normally 2kW) as you have a combi boiler.

Gas usage in summer low but in winter it is 1 to 1.5 therms and in winter 3 to 3.5.

Do you mean kilowatt-hours?

 

[boss_cat2]

In terms of usage, I believe to convert a Therm to Kw the conversion factor is 31.75. I tried the site, cheers, got 22 Kw, this suggests to me that we have sufficient capacity.

31 kW is probably OK. But, to be on the safe side, use the Whole House Boiler Size Calculator using your current house dimensions, then add in the known heating requirement for the new extension. You should set the Hot Water allowance to 0 kW (normally 2kW) as you have a combi boiler.


Do you mean kilowatt-hours?