jack

What about when my ASHP is in cooling mode?

Those national house builders who are renowned for poor workmanship and corner-cutting? Perhaps not surprising if they aren't getting good results. Hopefully you plan to build and insulate better than these builders. I think the main point people are making is that nothing he says seems to make sense. He's flat out wrong on the hydrogen boiler theory, and his comments about ASHPs are completely at odds with the experiences of most BuildHub members. These numbers don't add up unless they're running massive arrays. To give you a concrete numerical example, I live in the south of England and have 8.5 kW of PV on the roof. I average maybe 150 kWh/month in December and January. That's 5 kWh/day, although the median is lower than that. Put another way, that's 5 hours of a 1 kW electric heater. I'm pretty sure any dwelling in Scotland is going to need a huge amount more energy than that to remain comfortable through winter. As an example of how bad things can get, here's December 2021: Output rises above 4 kWh/day only a handful of times, and is regularly below 2 kWh/day. As another comparison, my electric car has a 38 kWh battery (that's actually on the small side - Teslas have between 50 kWh and 100 kWh batteries). Assuming 100% efficiency, my panels could charge my car 3-4 times a month in winter, assuming I don't use the energy for anything else. To achieve even these theoretical numbers, I'd need a battery system connected to the PV array, because the array itself rarely outputs enough power in winter to charge a car (car chargers have a minimum charge power of something like 1.2 kW, so if you can't get that from the array or a connected battery, the difference will need to be made up from the grid). And that's based on an 8.5 kW array in the south of England. The same array will do considerably worse in Scotland. You really need to do the numbers based on heating demand calculations for your proposed property. Edited to add: I forgot to include this link, which you might find interesting: http://euanmearns.com/solar-pv-potential-in-scotland/

I barely know where to start with this. What did he say was wrong with heat pumps (ASHPs as we tend to call them)? Many BuildHub members have ASHPs and are very happy with them, myself included. It's interesting that he sells and installs ASHPs for housing associations - are these retrofits and/or poorly built/insulated housing by any chance? Or maybe he or the company he's involved with don't actually know what they're doing and are undersizing what they sell/install for their customers. I can't think of any other reason someone would be so anti ASHP. As discussed repeatedly on BuildHub, hydrogen is unlikely to have a future in supplementing gas for boilers: As for infrared heating panels, they have their place, but primary heating for an entire home probably isn't it. That he's suggesting solar can be relied upon for providing significant energy during the heating period anywhere in Scotland is concerning. Solar panels won't output much in the depths of winter in Scotland, even on the best of days. Sorry to be so negative about your family member, but I'm really struggling to see how any of the advice he's given makes any sense.

Concrete or tiles should be fine (assuming no chipboard or OSB underneath). I suppose if there was enough condensation within grout for a long enough period you could get some mould growth, but at the sorts of temperatures we're talking about that doesn't seem likely. There's an increasing risk the more mould prone the final surface or substrate is. Also, the more insulating the substrate, the less effective the cooling. We have one carpeted room downstairs, for example, and it's the hottest room in summer and the coldest in winter, as a result of the carpet and underlay (not low-TOG) insulating the underlying slab from the room.

I wouldn't worry about looking for drawings to set up underfloor cooling. It's literally exactly the same as UFH. The only differences when cooling instead of heating are: - You need to figure out how to enable cooling mode on the ASHP. Varies by manufacturer and model. - If you want to have the cooling controlled by a thermostat, I seem to recall that you may need a second thermostat for cooling operation, or at least a thermostat with both normally open and normally closed outputs. One output is connected to call for heat, the other is connected to call for cooling. I personally don't bother with a thermostat in cooling mode. I have the ASHP outlet temp set to about 15° C in cooling mode, and that seems to result in the (polished concrete) floor settling at around 19° C. During long warm periods, I run it during the day when the sun is up so it gets assistance from our PV. During the worst of the recent heatwave I left it on 24 hours a day for about five days, including a couple of days before the really high heat hit. Worked really well.

@Steve247, there was an event posting that mirrored the wording above. I assume it was unintentional, so I've hidden it. On the topic of underfloor cooling, there's nothing in the standard Wunda setup that will prevent its use for use with an ASHP in cooling mode. They just don't want to be responsible for someone running their cooling at well below the dew point under wooden floors, and being sued a few years for water damage caused by condensation. I have a standard Wunda manifold and pump set (admittedly from about 6 or 7 years ago) and it works perfectly fine to cool our insulated slab with polished concrete overlay.

Bad maths, meant a quid.

That's a 3 kW kettle element for an hour a day, or about £0.30 a day at current rates. Doesn't seem wildly excessive given the volume of water being heated.

I believe they only module down to a certain point though. If that point is too high, you could have cycling problems.

That seems high. Was that the building regs calculation? Our house is 289 m2 (with 2.85 m ceilings downstairs, a double height area, and 2.5 m ceilings upstairs, so probably higher volume than average for the floor area) and I think the BR calculation was 180 m3/h. In general, the BR requirements ventilation rate is far too high imo. I know that several people on BuildHub have cut that rate by half (or more) without any issues.

I generally run the MVHR at a fairly low default setting (80 or 100 m3 per hour, from memory) all year round.

Following on from my earlier comment about being surprised that it wasn't sweltering upstairs the night before last, I had the same experience last night. Back-to-back hottest days on record after a week of high and increasing temperatues, and it was still only a bit warm upstairs. Perfectly comfortable to sleep with a pedestal fan on low. I can only assume that by getting the underfloor cooling on early and leaving it running 24 hours a day for the last handful of days, the temperature upstairs hasn't had a chance to get out of control. It's a puzzlement.

Crazy. It takes hours for underfloor cooling to bring the temperature of the whole space down. 24+ hours would have been a better test period. Well here's the funny thing: I hadn't been upstairs during the day, and guessed 30+ based on the temperature the night before and the fact we had an incredibly hot day yesterday. However, when I went upstairs last night, I was surprised to find it only warm, not ridiculously hot. If anything, it felt like the temperature hadn't moved at all from the night before, and I'd be surprised if it was 30 degrees. Best guess is probably 26 or 27. The only things I can think that might have caused this are: it was overcast here a lot of yesterday, meaning solar gain was lower. I've had the underfloor cooling running 24 hours a day for the last three days, and that's having some impact on the temperature upstairs even though it's only directly cooling the slab downstairs. There'll be a small amount of cooling from the effect of cold air from downstairs mixing in the MVHR heat exchanger, but that alone surely can't explain the difference.

I run my UFH at 25, and it's only that high because I can't turn it lower. I have a small amount of weather compensation dialed in - from memory, I think it starts kicking in at about 7 or 8 degrees outside temp, and ramps the outlet temp to 28 or 29 degrees at around 0 degrees outside temp. I'm sometimes curious about what it would have been like to have radiators rather than UFH in an airtight and well-insulated house. That said, I certainly don't miss having big lumps of metal all over the walls!

I haven't watched the whole video, but how long did they allow the house to cool before deciding it didn't work that well? I don't have temp sensing, but at a guess it's currently something like 20º C downstairs, with a 16º C outlet temp from the ASHP. Coming in from outside feels like walking into a deep, dark cave. It got to 37º C here earlier today, and it's got to be over 30º C upstairs. Perhaps the cooling effect won't be so pronounced in a bungalow, given you have a warm ceiling immediately above the cooled floor. That said, even if you only get a 5º – 6º reduction, that could easily be the difference between a tolerable 22º C and an uncomfortable 28º C. I know which temperature I'd prefer to be sleeping in!

Ah, that sounds like positive pressure ventilation. Try putting this search term in google: positive pressure ventilation site:buildhub.org.uk Incidentally, positive pressure ventilation isn't considered MVHR, because it doesn't include heat recovery (= the HR in MVHR).

It's different for different people. For example, some think the forum is about unpaid volunteers giving up their time to help people. For others, it's about snapping at people trying to help, just because they don't like the answers they're getting.

I've never heard the term "insufflation" used in the context of building ventilation. Is this some sort of positive pressure ventilation system?

Looking at the manufacturer's code in the tech spec drop-down, I'd be surprised if there's any difference other than length: Odd that they're described so differently.

The surface area of the pipe exposed to the sun is less than that of the pool as a whole. You might be better off putting thick black plastic in the bottom of the pool, and maybe some bubble wrap on top of the water when it isn't in use. The heat is directly transferred to the water, so fewer losses and no need for a pump. Plus more surface area, so more energy. It might be more effective if you mount the pool on the PIR.

I half-heartedly looked into exactly this when we were thinking about how we would heat our house, but quickly stopped when I saw the results of the initial calculations.

I've always used: uk-water-softeners.co.uk Good prices and they do their own deliveries (although the delivery area is limited because of this).

I doubt you need to break solid rock down to the full depth, but there's likely to be a minimum depth of hardcode to ensure load distribution. Only the engineer responsible for the design can confirm.

I doubt you're the only one who thinks this, but I disagree. "Battery" has a long history of use in relation to thermal storage. Chemical storage devices of the type you're referring to are only called batteries because they're formed from a battery of cells.

Any home automation system that requires you to get your phone out more than once a week is a poorly designed and/or implemented home automation system imo. I rarely use my phone to control anything. All lights are on physical switches (but some of the switches do different things depending on time of day). Blinds are mostly automated based on time of day (except in the bedrooms), but also have switches for manual control. I've had similar, but generally waving your arms around was enough. It's worse in a large office unless you're willing to install lots of presence sensors. I mainly haven't bothered within presence sensing due to cost. Decent ones cost tens of quid, and the insane payback time means it makes no sense for me to install them.