Andehh Posted October 29, 2022 Share Posted October 29, 2022 (edited) Due to a cock up on my part, our windows are 1.6u NOT the 1.3u the window company has been telling me for several weeks. They were quoting glazing-only figure, and I took it as whole window figure. I've only found this out 2 days prior to delivery so nothing I can do now sadly - to say I am gutted is an understatement. To make matters worse, this drops us from an A SAP down to 'only' 91 SAP - a B. We have 3.99kW of Solar going in (already on site), roof, walls, floor are already built. We already have Solar diverter going in for hot water, have got good MVHR & ASHP (actuals used in SAP).... and i'm out of ideas on anything else we could get in to find that extra 1 SAP point - reasonably priced or so. We are 'as design of 5' air tightness, which I have been fastidious at trying to reduce, so i'm hoping that might help....but hoping for any other ideas people might have? Edited October 29, 2022 by Andehh Link to comment Share on other sites More sharing options...
SteamyTea Posted October 29, 2022 Share Posted October 29, 2022 (edited) Can you add secondary glazing on a few windows (North facing maybe). Add more PV (if DNO allows). Make sure heating has controls that lower energy usage. More loft insulation. Waste Water Heat Recovery. Edited October 29, 2022 by SteamyTea Link to comment Share on other sites More sharing options...
Dave Jones Posted October 29, 2022 Share Posted October 29, 2022 put one of these heat recovery units under the bath, cheap and easy SAP points, save you money as well. https://recoupwwhrs.co.uk/products/easyfit/ 1 Link to comment Share on other sites More sharing options...
Conor Posted October 29, 2022 Share Posted October 29, 2022 (edited) A good airtight test result will get you a much better score. Get the SAP person to re-run at an infiltration rate of 3. If you've been paying attention to quality and taking basic airtight measures, you'll get less than 2. Are the windows ordered/installed? They sound very poor performing. You'll notice that in summer and esp winter. Ours ranged from 0.5-0.9. Edited October 29, 2022 by Conor 1 Link to comment Share on other sites More sharing options...
ProDave Posted October 29, 2022 Share Posted October 29, 2022 9 minutes ago, Andehh said: We are 'as design of 5' air tightness, which I have been fastidious at trying to reduce, so i'm hoping that might help 5 is pretty poor. Get an actual air tightness test done and if you get a substantially lower score that will give you the extra points you need. Otherwise the heat recovery unit mentioned above. Link to comment Share on other sites More sharing options...
Andehh Posted October 29, 2022 Author Share Posted October 29, 2022 (edited) Thanks very much all....that's good to know. I have been very hot sealing up every gap I can think of, and will do so again after windows go in. Having a bungalow with warm roof & a builder who is used to seeing me up the scaffolding with expanding foam in one hand & silicone in another has made it a bit easier (I know neither are fool proof, but I am thorough to a fault with them both - inside & out). We could ask about secondary glazing, the reality is we will have blinds & curtains in every window tightly fitted, so the actual impact cost wise will be minor...its more the SAP & ''points mean prizes!!'' focusI have Ill speak to build about Waste Water heat recovery.... the drainage is all in, but shower trays not installed/poured, so ill have to check with them on how we make it work. If anyone is able to share their experiences of what ait tightness did to their SAP / EPC (before & after) report I'd be grateful??!! - thanks in advance Edited October 29, 2022 by Andehh Link to comment Share on other sites More sharing options...
PeterW Posted October 29, 2022 Share Posted October 29, 2022 @Andehh your airtightness is your friend here - and you need to do the test just after the windows go in and before they start on boarding out and covering all the holes up. You may even want to do 2 tests - you can rig your own blower door too using an old car fan or even hire a test rig and then go looking for all the gaps - easily spotted and you will pay dividends when the actual test is done with this approach. If you have a block skin inner you may also benefit from a parge coat of sand & cement or bonding applied with a broom to seal up all the gaps in blockwork. It’s a few hours job but not expensive and well worth the effort as finding the gaps will be nigh on impossible when you’ve got the boards up and skimmed 2 1 Link to comment Share on other sites More sharing options...
Andehh Posted October 29, 2022 Author Share Posted October 29, 2022 Thanks Peter - some of our walls are 4.5m tall to ceiling so that would be tricky. I have gone over every inch of wall & roof interface (and will do for the windows) filling to ensure all sealed up tightly, same with every hole passing through the block work sealing the inside & outside. Its something I continue to monitor & adjust. Thanks for all the feedback though Link to comment Share on other sites More sharing options...
saveasteading Posted October 30, 2022 Share Posted October 30, 2022 On 29/10/2022 at 09:07, Andehh said: Waste Water heat recovery I'd say forget it. The waste water goes out as fast as you can make it, and it is very complex, and expensive, to try to use it to heat incoming water or air. For example i once saw a shower tray designed to warm the incoming cold water. It was clever, but involved a lot of pipework, a big hole in the floor, and the routing of the cold feed under the tray. Leaving the bathwater to cool into the room is as far as i would go. On 29/10/2022 at 09:26, Andehh said: walls are 4.5m tall to ceiling A fan will bring the excess warm air down to the floor from the ceiling. If switched to blow upwards it also avoids the feeling of draughts. Call it heat recovery and award yourself some sap points. Link to comment Share on other sites More sharing options...
Dave Jones Posted October 30, 2022 Share Posted October 30, 2022 2 hours ago, saveasteading said: I'd say forget it. The waste water goes out as fast as you can make it, and it is very complex, and expensive, to try to use it to heat incoming water or air. For example i once saw a shower tray designed to warm the incoming cold water. It was clever, but involved a lot of pipework, a big hole in the floor, and the routing of the cold feed under the tray. Leaving the bathwater to cool into the room is as far as i would go. A fan will bring the excess warm air down to the floor from the ceiling. If switched to blow upwards it also avoids the feeling of draughts. Call it heat recovery and award yourself some sap points. its actually none of that... payback in 1.5 years. Link to comment Share on other sites More sharing options...
SteamyTea Posted October 30, 2022 Share Posted October 30, 2022 2 hours ago, saveasteading said: I'd say forget it. The waste water goes out as fast as you can make it, and it is very complex, and expensive, to try to use it to heat incoming water or air. 1 minute ago, Dave Jones said: its actually none of that... payback in 1.5 years Has anyone seen independent data for waste water heat recovery. Intuitively I feel it won't be brilliant, but never modelled it, and no one I know who has one, has actually measured it. I feel it falls into the same category as co sensing boiler efficiency and multi foil insulation. They work, but never get close to the headline figures. Link to comment Share on other sites More sharing options...
Mr Punter Posted October 30, 2022 Share Posted October 30, 2022 5 is fairly poor for airtightness. 3 is easily achieved. 1.6 for the glazing units is really very poor. Can you ask your SAP person for suggestions? Sometimes extra boiler controls can make a difference to the score. I assume you need the points for a mortgage? I see some of the housebashers doing waste water heat recovery so I guess it must be a fairly cheap win. You can get an airtightness test done once the windows and doors are in and sealed. Probably change of £200 and you can identify any weak points. Do it before you plasterboard. Link to comment Share on other sites More sharing options...
saveasteading Posted October 30, 2022 Share Posted October 30, 2022 1 hour ago, Dave Jones said: payback in 1.5 years. Interesting. More detail please or direct me to the info. Link to comment Share on other sites More sharing options...
ProDave Posted October 30, 2022 Share Posted October 30, 2022 This water heat recovery thing. When I have a normal length man shower (could be different for a long lady shower) when wiping down at the end, I find any water left is "cold". My assumption being most of the heat in the hot water has been absorbed by it landing on the "cold" (room temperature) walls and floor. So most of the heat is being absorbed by that, later to be released back into the room. It would be interesting to lower a waterproof temperature probe into the shower trap and read the actual temperature of the water reaching the trap. My suspicion is it will be a lot lower than the shower water temperature, so any theoretical heat recovery will be less than expected. Like @SteamyTea I would like to see data. Link to comment Share on other sites More sharing options...
saveasteading Posted October 30, 2022 Share Posted October 30, 2022 Seems these shower units cost about £500, then add for plumbing in and building into the floor (and insulating!). SAY £800? Prob not enough but helps the sums. One manufacturer claims £20 saving per user per year. 4 users means 10 year payback. So worth considering. Would need to see proof though, as cynical me thinks perhaps it is an easy way to buy sap points on a project that would better be redesigned. Link to comment Share on other sites More sharing options...
ProDave Posted October 30, 2022 Share Posted October 30, 2022 8 minutes ago, saveasteading said: So worth considering. Would need to see proof though, as cynical me thinks perhaps it is an easy way to buy sap points on a project that would better be redesigned. How many extra SAP points would an extra £800 of PV add? Link to comment Share on other sites More sharing options...
dpmiller Posted October 30, 2022 Share Posted October 30, 2022 I fitted a Zypho unit under our most frequently-used shower back whenever they were a sensible price, although they're still not bad where I got ours... https://www.greentherm.ie/product/zyphoizi-shower-waste-water-heat-recovery-unit/ Link to comment Share on other sites More sharing options...
jack Posted October 30, 2022 Share Posted October 30, 2022 If we accept the 80% (or even up to 90%) recovery figures for MVHR at a high airflow rate and a typical temperature difference of perhaps 15-25 deg C, 50% recovery in a heat recovery system of this type given a temperature difference that's typically at least as high doesn't seem so unlikely. The main thing that bugs me about the idea is the likelihood of biofilm building up on the inside of the pipe, which would reduce performance. I'd planned to inspect and clean mine every year or two, but have never managed it in 7 years. Perhaps I'll do some experiments if I get the time in the coming weeks (Narrator: "There's no way he'll get the time") Link to comment Share on other sites More sharing options...
ProDave Posted October 30, 2022 Share Posted October 30, 2022 16 minutes ago, dpmiller said: I fitted a Zypho unit under our most frequently-used shower back whenever they were a sensible price, although they're still not bad where I got ours... https://www.greentherm.ie/product/zyphoizi-shower-waste-water-heat-recovery-unit/ That estimates a waste water temperature of 27 degrees. My point above is I would be very surprised if the actual water going down the plughole is that warm after the room and walls / tiles have taken some heat out of it. Link to comment Share on other sites More sharing options...
Radian Posted October 30, 2022 Share Posted October 30, 2022 1 hour ago, ProDave said: That estimates a waste water temperature of 27 degrees. My point above is I would be very surprised if the actual water going down the plughole is that warm after the room and walls / tiles have taken some heat out of it. If the water running down your legs and feet wasn't at least 27oC I'd bet you would leap out cursing about having an unexpectedly cold shower. 😃 1 Link to comment Share on other sites More sharing options...
Andehh Posted October 30, 2022 Author Share Posted October 30, 2022 Thanks very much all, yeah windows poor but in stuck with them now. They are very slim aluminium and always knew they'd be a compromise, was just hoping for closer to 1.3 which I was told they were... Just omitting the (expletive deleted)ing frames when confirmed it with me. I'll ask SAP if waste water would help, if not ill leave it. Can't add more PV as existing is tied into a good tariff and can't be changed. Hoping for much better then 5 air tightness wise... Anyone estimate what SAP improvement going from 5 to say 3? Thanks again all Link to comment Share on other sites More sharing options...
SteamyTea Posted October 30, 2022 Share Posted October 30, 2022 7 minutes ago, Andehh said: Can't add more PV as existing is tied into a good tariff and can't be changed. Can you directly supply a storage vessel without it being grid tied? Should be able to keep your existing tariff as it is technically off grid. Link to comment Share on other sites More sharing options...
ProDave Posted October 30, 2022 Share Posted October 30, 2022 27 minutes ago, Andehh said: Can't add more PV as existing is tied into a good tariff and can't be changed. Yes you can, just make sure it's a separate inverter and not connected through the FIT meter, so you have not altered the original FIT kit. Link to comment Share on other sites More sharing options...
PeterW Posted October 30, 2022 Share Posted October 30, 2022 34 minutes ago, Andehh said: Hoping for much better then 5 air tightness wise... Anyone estimate what SAP improvement going from 5 to say 3? probably 3-4 points - ask your SAP assessor or plug it into the model (assuming they sent it to you..?) Link to comment Share on other sites More sharing options...
jack Posted November 1, 2022 Share Posted November 1, 2022 On 30/10/2022 at 19:16, Radian said: If the water running down your legs and feet wasn't at least 27oC I'd bet you would leap out cursing about having an unexpectedly cold shower. 😃 On 30/10/2022 at 16:43, ProDave said: It would be interesting to lower a waterproof temperature probe into the shower trap and read the actual temperature of the water reaching the trap. My suspicion is it will be a lot lower than the shower water temperature, so any theoretical heat recovery will be less than expected. I stuck a temperature probe into the trap after showering this morning. The temperature was 34.6 ºC. You might lose some heat to the drain before the water enters the WWHR unit, but 27 ºC doesn't sound unreasonable for modelling purposes. 1 Link to comment Share on other sites More sharing options...
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