nwnw

@JohnMo you're right, more detail required...below is a rough layout of existing and new. Open plan area will be almost doubled. Intention would be to have a small radiator in each of the new well insulated Entrance and Utility rooms. It's the extended living area that I think would benefit from UFH. As I say, there's also an open stairway so with radiators I practically need to heat upstairs before downstairs gets warm, although nowadays with the ASHP on all the time it's not such an issue. My thinking is that I wouldn't need/want to fill the entire new floor with pipes. In theory I just need to replace the heat from an existing 1200x600 K2 radiator that will be removed along with the wall and maybe a bit more to help reduce the flow temperatures from my ASHP (and hence improve efficiency). "Power Output at Delta 50" for the K2 rad removed is about 2080W. So if I assume that I want, say, 3500W Power Output at Delta 50 for the UFH then how do I go about detailing the pipe length, size, spacing? How do I determine if a single loop is sufficient? And how do I determine if the ASHP pump is up to the job? Worth noting that I will still have another 1000mm K2 radiator in the existing living space, and if I find the ASHP flow temps are then too low for the rest of the house then I can always switch that off (until I upgrade some rads elsewhere in the house). Hope that makes more sense now.

18 months later and I'm revisiting the subject of UFH vs radiators. I had my heat pump installed last August and it has been a revelation. Warm house all year round. Much much cheaper to run than my old oil boiler (I have solar and a battery also, which helps a lot). I didn't rip up the floor and install UFH. Basically my radiators work exactly as they were (one bedroom rad was upgraded, but that was it). My extension is now going ahead next Spring/Summer. This will add about 50m2 of living space, but will be very well insulated so should not add much wrt heat demand. The extension work will remove a large section of wall (to make open plan with existing living space) which will also eliminate a large radiator. There will not be much free wall space in the new space. So, my quandary is, do I play it safe and cram in a couple of radiators as big as I can make them in the new space? Or do I install a single loop of UFH in the new space (I'm having a 150mm slab floor so can easily attach to the reinforcing mesh)? I still like the idea of UFH in the living space, to give an even, comfortable heat with less of the heat disappearing upstairs (open stairway in the living space). Can I run a single UFH loop basically as I would a large radiator if I size it right? (I.e. fully open, without an extra pump, throttling, etc) The ASHP is effectively on 24 hours a day so lends itself to this. Are there any good calculators for UFH sizing? (note that I will have 15mm engineered wood flooring on top). Any pitfalls?? My only worry is that if oversized on the UFH, the flow temperature could lower to a point where the rest of the house doesn't get hot enough (which might take me back to fans on radiators!).

I was reading posts on this recently and it seems that Envirograf is generally cheaper than Tenmat. However, I did see that folks were getting away without using intumescent strips if they had an open 'rain screen' cladding format, which is what I'm looking at. Will need a chat with BCO.

Hi folks, I'm working on the design for a new extension (all in Sketchup). Loads of queries to come and I'll probably put my drawings up here soon for scrutiny. My biggest headscratcher just now is how to support the existing roof structure when I remove a 6.5m length of structural stone wall. I've seen various ways to do this with joist hangers and sandwiching timber on the steel, but I'm wondering why I can just mount direct as shown below. I've coloured for clarity...Blue = existing roof trusses and joists. Red = new extension flat roof joists and firrings. Pink = Steel Existing timbers I'm sure will not be perfectly aligned so my thinking would be to leave a nominal gap and shim to the steel, or to profile the face and underside of the joists a tiny bit to fit. Thoughts?? Pitfalls??

This got me thinking...does a product exist that simply adds fans to the top of standard radiators to perform this function. Indeed, quite a few seem to exist, although they all seem to be cheapish and a bit of a hash-job. E.g. https://radiatorfan.co.uk/radiator-fans/ I did find a very interesting report on experiments that were carried out on radiator fans... https://www.sciencedirect.com/science/article/pii/S2214157X23007384?ssrnid=4513816&dgcid=SSRN_redirect_SD They found that the 337W of a std convector radiator at 40degC was increased to 616W at normal fan speed and 1173W at higher fan speed. Good empirical proof that they work as you would expect. It states that the effect is greater at lower flow temperatures, so lends itself well to ASHP heating and I wonder if these are a good way around fitting bigger rads. It would also be easily removed if it was found that the MCS heat demand estimates were overdone. Anyone have any experience of these?

I may be adding confusion. If I was going for UFH then I would be digging out and installing thicker insulation. The 30mm was just to be laid on top of existing slab. I'll need to recalculate the room demand based on the extra insulation to see if the rads need upgrading.

I was assuming that you need special insulation for the compressive strength, but I guess the battens get around that. Thinking further about this though...the battens will likely create thermal bridging points in the insulation so am I possibly better off with XPS or PIR that has greater rigidity and doesn't require battens? Also easier to install and cheaper. I see Kingspan Thermafloor comes in 30mm.

The realisation that I probably can't lower the flow temperature as I still have rads in other rooms has got me thinking again about UFH. I would still love to put some insulation in though - and this may help bring the room demand down such that I don't need a massive radiator (or multiple plinth heaters!). Is there good insulation that can go directly under wood flooring? There is a slight step down to the living area so I could install to 30mm without a massive impact.

For reference it's a stone walled, detached house. Built about 1880 I think. Walls are about 50-55cm thick, I assume rubble filled. My point was that the walls were there long before a cement floor was laid, so it should be in no way structural. If I was digging out then I would intend to taper in (45 deg?) at the edges and ensure that I am in no way compromising the wall foundations.

I think the floor was relayed in 2006 when the house was reconfigured. The stone walls have been standing for 120 years before that so I think will be fine as long as I don't undercut the founds. Although I guess given the age it was probably built straight on the ground.

Ah, ok sorry. Had a look at the SS5 and at 45degC ASHP temps it only puts out 0.6kW at the 'normal' setting (or 1.1kW at 70degC). The existing double convector in my living area is rated at 2kW. So I guess I would need at least 2. I assume the heat from them is better distributed, given that it is blown rather than convected?...what are people's experience of this? Or do they create a 'wind-chill' effect?

Direct electric? I prefer the idea of a 4+ COP over the next 25 years. 🙂

I had quotes for exactly this a year or two ago. Since then my oil-fired boiler has had numerous issues (to the point of needing replacement asap) and I've also realised that I can get a £9000 grant for a full ASHP (sadly no grant for air to air)! The thinking behind the UFH was that it's also a chance to stick in 100-150mm insulation. The heat demand survey shows a huge loss through the floor.

Ah, I was wondering that and have already asked the installer this question. My assumption was that the flow temperature could somehow be reduced for an UFH loop. I guess it just reduces the flow instead?

I've just arranged for quotes for installing an ASHP to replace our ageing oil-fired boiler. I highly suspect they are going to come back and say that our radiators in the living space are too small and would need replaced. For that reason, and for general comfort/insulation, I am considering retrofitting UFH for the living space. The floor is currently wood on concrete, redone in 2006 and I assume uninsulated. I would do an 'exploratory hole' to check this before proceeding! The room is 5m x 4m. My first thoughts are to lift the wood flooring, dig out the concrete to required depth (up to edges but not affecting founds), flatten with hardcore, lay insulation (100mm or 150mm PIR/PUR?) + DPM, lay UFH pipework and encapsulate in a 60-75mm concrete slab, re-lay wood floor. I'm not sure that I would be able to have insulated upstands at the edges so I guess I would keep the UFH pipework inbound a bit more (500mm?) to reduce the thermal bridging. Anything I'm missing or need to be aware of before speaking with installers/builders? E.g. is it a good idea to be mixing UFH with radiators (in all other rooms)?