osprey Posted March 5 Share Posted March 5 I am driving myself crazy going around in circles with this, so am appealing for opinions. I can't settle on a heating scheme for my house/extension. I want to future proof it if possible, but do not want a cold house, obviously. Current house is 1926 build, 50mm cavity, outside rendered, two story detached. Suspended wooden floors. Floor plan is 'L' shaped, 10m on long sides. I am planning a 5m × 5m extension, to make the footprint square, which will create a 10m x 5m kitchen/utility/dining area. The 5 x 5m extension will be 150mm cavity eps beads, floor block&beam. The house has had its 50mm cavities filled with blown eps beads, and the old kitchen area will have 50mm IWI added during extension build. It is possible, in the future, to add 50-100mm EWI to the house side walls. The front has bay windows, making EWI impracticable. I have added 100mm pri under one existing room, and plan to do the second. Hall will be done when extension is built. So, question: UFH to extension+kitchen? Whole ground floor? Stick with radiators? Rooms have 2.8m ceilings, so can take 20mm or so build height of retrofit UFH, but have heard various stories (positive and negative) of effectiveness in old houses. Current Lounge has carpet, which I would like to keep. Thanks. Link to comment Share on other sites More sharing options...
JohnMo Posted March 5 Share Posted March 5 With 100mm insulation stick with radiators, but oversize for low flow temperature. You really need 150mm (ground bearing) insulation under UFH to make viable from a downward heat loss perspective, block and beam makes matters worse with downwards heat loss. Assuming you have a gas boiler get that changed to run X plan if you can, one temp for hot water and the other weather compensation for heating. 1 Link to comment Share on other sites More sharing options...
jayc89 Posted March 5 Share Posted March 5 We had rotten floor joists so replaced with a slab and UFH. Fitted 100mm PIR as advised by a builder at the time, and wish we'd gone thicker, will be doing so for the extension. It's certainly no more expensive than rads though, and IMO is a far superior distribution of heat. 1 Link to comment Share on other sites More sharing options...
osprey Posted March 5 Author Share Posted March 5 @Johnmo Interesting. I know the more the better with insulation, but I understood 100mm pir was enough for retrofit. The new block and beam floor will have whatever insulation is required for Part L, I guess: would it still be worse? Yes, gas boiler, that will be replaced anyway. Thanks for constructive comments. Link to comment Share on other sites More sharing options...
JohnMo Posted March 5 Share Posted March 5 2 minutes ago, osprey said: 100mm pir was enough for retrofi Depends if the person saying 100mm is ok, is the one that has to pay the bill, for the additional downwards heat loss. 3 minutes ago, osprey said: gas boiler, that will be replaced anyway I would treat be boiler in the same way you would a heat pump. Design the radiators for a max flow temp of 35 to 40 deg, they will be big and never feel hot, but you basically run them continuously on weather compensation, house is always warm. Also if you are installing a cylinder, get a heat pump one installed with a 3m2 coil. X plan will allow two different flow temps to be used, both set to get the best form the system. Some reading material https://www.intergasheating.co.uk/homeowner/2022/07/13/the-knowledge/ Link to comment Share on other sites More sharing options...
osprey Posted March 5 Author Share Posted March 5 @Johnmo Doubling the size of the rads would be problematic: they would start to dominate the room! They were probably sized for the house with no insulation, and CWI has allowed me to keep warm with flow temperature of 50-55c this winter (and we had a few cold days) but 40c would be pushing it.. 15mm pipe feeds to all (off larger distribution pipes). Link to comment Share on other sites More sharing options...
JohnMo Posted March 5 Share Posted March 5 14 minutes ago, osprey said: Doubling the size of the rads Depending on what's installed now, adding fins or extra panels keeps the radiator size but increases output as if the radiator is bigger. The lower the return temperature to the boiler the better efficiency you get. Also see https://www.heatgeek.com/does-my-pipework-need-upgrading-for-a-heat-pump-with-cheat-sheet/ Link to comment Share on other sites More sharing options...
osprey Posted March 7 Author Share Posted March 7 By the way: are we just talking about traditional UFH (buried in thick screed)? Retrofit overlay UFH suppliers claim they are more 'radiator-like' in that they respond quicker, and can handle higher temperatures (high 20c's?) depending on floor covering. Link to comment Share on other sites More sharing options...
JohnMo Posted March 7 Share Posted March 7 20 minutes ago, osprey said: handle higher temperatures (high 20c's?) More like flow temps in the 40s, I had some in my well insulated summer house (now ufh decommissioned because it was rubbish), high 30s flow room below 16. Link to comment Share on other sites More sharing options...
osprey Posted March 7 Author Share Posted March 7 Interesting. Any idea why it didn't work out? Link to comment Share on other sites More sharing options...
JohnMo Posted March 7 Share Posted March 7 Was driving the UFH from a heat pump, and flow temps needed to be higher than I was prepared to run. Now use a fan coil, way better. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now