joth

IKWYM - they're slowly working their way around our town, but say they have no plans to do our street. I think it's because we're in a conservation area and all the cables are underground. Most the town is on overhead pylons and it seems relatively simple for them to pull the fibre to each pole, and then drop it into individual houses as and when requested. Unfortunately our contractor accidentally ripped the old OR copper cable out when digging the soak away, so I'm now on the fence if I get them to pull a new copper wire in anyway. We're currently on VM but with 2 of use working from home both days now, having a redundant fail over seems tempting. (Last time I needed it 4G failover was not a success last time I needed it, as too much of my setup did not like being behind carrier grade NAT)

I imagine everyone here assumes you're after triple glazed windows with no trickle vents, and installed fully airtight between the frame and the building. Note that none of those things are standard practice or ensured by building regs / Fensa certificates, so if this is not what you're looking for you may need to spell out the building performance requirements a bit more.

Bear in mind that if the towel rads are all over the house, and if it's a well insulated house, this could add quite a bit to summer overheating. If you do do that obviously insulate all this extra pipework We decided just to go with electric towel rads, and not plumb them in at all. I have them set to run for 40mins after anyone uses the shower/bath, and remain turned off the rest of the time, to avoid any unnecessary heating.

An alternative approach is to use an enthalpy heat exchanger (So "energy recovery" rather than heat recovery) and then you don't need a condensate drain. BTW depending what other things you have in the utility room, you may need more drainage anyway? I was surprised by the number of tundish and overflows needed for heating system, water softener, etc, and with condensate dripping off basically everything when using active cooling I kinda wish I'd just tanked the room and set a drain into the tiled floor.

Is the garage inside the airtightness & thermal envelope? Normally they're not as an airtight garage door is borderline impossible. But putting the MVHR unit outside the airtight boundary will be awkward as it's (potentially) a lot of pipework to detail airtightness for (depending on manifold locations etc), and also the unit is more efficient if inside the thermal envelope and any warm-side ducting outside the thermal envelope would need to be insulated. tl;dr: Utility room is likely the better choice.

Yes, that's why said "all else being equal" (or at least attempted to, sorry about the typo). This is exactly what the calculation in my original post is accounting for. 1 ACH is shifting 10W per °C difference in temperature between the supply air and the room temperature, which is effectively negligible for removing the 160W of body heat. Even in bypass mode in winter it's rarely going to exceed 150W so only just keep up (and of course, we'd not use bypass mode in winter, so in practice it's only around 10W in winter and a bit more in summer, on cool nights at least. Hence why with very efficient heat recovery, the overheating issue is actually going to be worse in winter than summer) I'm increasingly sure I don't

Can I check those units and values? Assuming 106 m3 then that's a substantial volume (vaulted ceiling?) -- about 3x our master room, so all else equally I'd estimate it'd take 3x as long for 2 people to heat up the air by 1ºC. It takes 2-3 hours for our room to get unbearable, so with a 3x larger room, I can easily see it getting through the night OK using daytime only purge. Obviously this will depend a lot on the outdoor temps overnight (worst case it'd actually be heating up the room by leaving the windows open) but for us, windows open makes a radically large difference. If it wasn't for the nearby train line, and wanting closed windows with triple glazing and additional sound insulation to block that out, this would be the solution (if a weird one to have to use in heating season) Well this year it was still unusually cold here in early May and my post was based on the very cold month + of experimentation leading up to that date. But yeah since then the experiment of sleeping in another room / house on a couple occasions has pretty much pinpointed it as a body heat issue. Also, the temperature graphs I have make it clear the temperatures sits stable when empty, but then starts to climb the moment the room is occupied. We also have a central atrium with a skylight that I now have automatically open when stack venting is required. This works like a champion for the house as a whole, but there's just not enough free airway from the bedroom to the atrium to balance out. I'm going to investigate putting a "chimney" like duct out of the bedroom feed up to a high point in the atrium near the skylight, to allow some passive circulation of air too (and also provide a better outlet for the forced-air circulation from the fancoil) Thanks for the replies, very helpful to know how others manage things in a passive (like) house

Yes, it does it on a whole building level, not room by room (AFAICT - I am not a PHPP expert). At the whole-building level we're totally fine - 2 people in a 4 bed house, no overheating experienced (except when there's a heatwave). The issue is on a per-room basis. PHPP has the "Heating Load" -> "Risk determination of group heating for a critical room", which a) does not have any allowance fort the largest source of heat in bedrooms, the occupants, and b) only deals with heating demand, not cooling demand. (The "Cooling load" tab has no such critical room risk calculator) It reports 3% overheating risk at 25 ºC. But again, this is a whole-house risk. What we see is 99% risk for one specific room, even on the days the rest of the house is sat at a nice comfortable 19ºC. Again, the internal insulation between floors and in the stud walls is actually hampering rather than helping here. No, and I really don't see it would help: My calculations in the OP say at MVHR circulation rates it would need to be delivering 4ºC air in order to keep up with 160W of heat source, which could only be achieved by having the ASHP running 365 days a year in cooling mode - very much against the ethos of a passive house! This is really interesting. Can I ask how the bedrooms specifically connect to the stack ventilation? e.g. do you have to open the bedroom windows to have this work ? And like ProDave, do you find you need to do this in the (occupied) bedrooms in winter as well as in summer? Or do you have some other way to promote more airflow through the room - besides the standard MVHR outlet and door gap - such that the bedroom windows can remain closed, yet still maintain a comfortable temperature? (or are the bedrooms particularly high volume, which would greatly increase the time it takes to warm up from body heat? or anything else that would aid this?) Thanks

Thanks! yeah done a few informal experiments with the thermal camera (challenge right now is getting the room cool enough that anything shows up), and also done the experiment with not sleeping in the room for a few days, and overall there's no issue with excess heat getting into the room from elsewhere. Your comment about insulation in the ground floor ceiling is really only relevant in the winter when the GF heating is on (when that insulation is inhibiting the flow of heat from the GF UFH into the upstairs bedroom). In the summer, it's much more about solar gains which can occur just as much in FF as GF. And given the GF is all open plan it's easier to "disperse" any solar gains coming in from one aspect, but in the FF it all gets boxed into the room its in and has to rely on MVHR to eventually blow it away, unless the doors or windows get opened. Anyway, the main issue is exactly as I mused in the original post: in 8 hours sleeping, 2 adults generate plenty enough heat energy to cause overheating that MVHR cannot shift on its own, and PHPP simply does not model this. Opening the doors/windows and/or adding additional fan ventilation is the only solution. The whole design process somewhat failed to flag this for us, but it's not impossible to retrofit (largely because I'd already planned for a fancoil blowing into the room anyway, I'm now working on wiring it up to operate in "fan only" mode as needed most nights) Cheers

The cheaper Flir one is only 80 x 60 resolution, compared with 320 x 400 for the one linked by @joth Exactly. The nearest I could find to this resolution from a "bigger name" manufacturer is the Seek CompactPro, which is 320 x 240 at £600. So getting almost double the pixels (320 x 400) for half that price seemed a bargain https://www.amazon.co.uk/Seek-Thermal-Compact-Resolution-Imaging-Black/dp/B01NBU1AVN 80 x 60 seemed totally pointless to me.

Sorry bad link above. This one: https://www.amazon.co.uk/gp/product/B07Y2V3SGG (no vested interest in it, just a happy customer)

Goodness how useful are these little beasts! Not the cheapest tool in the box, but I bought a Hti-Xintai HT-201 and really happy with it. Obviously will be useful for checking insulation detailing (although, best used on a cold night in winter), but my immediate use case was to figure out the source of an intermittent low level plastic melting smell coming from my AV cupbaord. Source turns out to be the 48V PSU for some spot lights -- internal temp getting to 110ºC but the majority of the case remained cool to touch. Pointing the camera in the cabinet and turning everything on, it lit up bright - instant diagnosis. For anyone doing a DIY home automation / tech / electronics install it seems a great idea to check for weak connections or other hotspots. Also highlights which of the little plug in wall warts run hot etc, can highlight any cables getting warm due to being near over current, trace out heating pipes, UFH loops etc. Nice little tool.

So I'm sure it will please you to know, it was reading your comments on this subject that pushed me over to get the Wifi version Thank you

Probably depends on the model no? Never seen this on ours, ~6 months old. Got the Wifi connected ones -- 90%of the motivation was so that the clocks would always be synchronised and accurate :))

Have you insulated all the supply side MVHR ductwork into each room? If not, you'll need to keep the temperature on the coil not so cold anyway, to avoid condensation forming in/on the ducts.

Before you disconnect electricity at the boundary, are you sure you don't want an electrical supply for build?? Normal procedure is to move the supply to a "temporary" site kiosk, and then you can leave it there indefinitely to avoid the cost of moving it a second time if you wish. (Also avoids putting a meter box in the exterior of the property, that can be unsightly and an insulation weak point) For the gas ... yeah cadent were bit of nightmare for us, £2k for similar reasons, which they delayed 5 months, then canceled on day of disconnect (this was at the start of lockdown), then did an emergency temporary disconnect and left that until a year later a leak in the street meant a team were working on repairs anyway and I had them finally do the perm disconnect under the road. (Which magically they managed in one hour without any traffic lights at all, after the original survey and quote said it would need full road closure in both directions, and be done on a school holiday due to neighbouring school. Go figure).

Nor are combi boilers, most people take very little interest in the sizing of them, or the flow rate they can produce. Quite true. I think it's useful to bear in mind this is how they're sold though, as it explains the mentality most are coming into ASHP with.

Absolutely, a "true" passive house just needs no ASHP, just few human bodies to heat it, right? At a more achievable level, a lot of people here see the economics of ASHP don't add up and go for a Willis heater for their wet UFH instead. Others want to protect themselves more against future energy price increases, or have non-financial reasons for going with ASHP (from reducing carbon output to enabling summer time cooling) Horses for courses. It's definitely not one-size-fits-all, not in the way that combi boilers are currently pitched. However, as sale go up, prices will come down, and it'll slowly capture more market share as the economics will gradually swing more in favour.

I'm using Unifi USG, their newer Dreammachine is pretty good for an entry level "prosumer" product. There's definitely downsides of their gear though, a search on here for Unifi might surface some of that. For a less technically demanding but robust consumer product, I have a lot of colleagues recommending TP-Link "Deco" mesh network products. Something like the Deco P9 3-pack is a good starting point, it has 2 gigabit eithernet ports plus integrated mains power line adapter in each AP, and creates a whole home mesh wifi network. Increasing number of wired LAN ports is just a case of plugging in an gigabit unmanaged switch like Netgear GS108UK

I think you have to use the Virgin Meida router, but it is more reliable if you switch it to "Modem Mode" and put your own IP router & wifi APs behind it. There are reports it is slower in modem mode though, I've not been able to prove this or otherwise. Either way, it's a piece of rubbish and runs at an absurdly hot temperature for what it's doing. I find VM have very variable latency and uplink speeds in particular. Different times of day, it's wildly different performance. I've never had that on any Openreach wholesale based product.

How is that not illegal? https://www.howatavraamsolicitors.co.uk/know-illegal-supplier-set-price-products-sold/

Just to emphasize this: it's worth looking into (15% saving on all the project costs) but there are severe restrictions: the property must be unoccupied for 2 years straight right up to the day the work starts, and all work must be done via a single VAT-registered contractor (as they apply the discount in their bill, there's no claim back) We missed out on this because (a) we thought our house was only unoccupied for 1 year prior to completion (it was actually 2), (b) we had no documented evidence of how long it had been unoccupied (council tax discount etc is the best for this), and (c) we moved into it on completion day, resetting the clock. If you want instant demand-heated hotwater, and not interested in (substantially) improving insulation of the property, an oil combo seems the only sensible choice.

> I was advised by the installer to run the heating 24/7/365… does this mean there should be pumps working all the time or that the system should turn on if a thermostat calls for heat? No the pumps shouldn't be running constantly, just that it should be able to call for heat at any time. Really shouldn't have to be 24 hours a day, but I expect their point is not to let the house get cold when out etc, and expect to heat up in half an hour when back. The FTC does have a timer built in which is fine if you don't want it running specific times, e.g. while sleeping Legionella cycle is disabled in the menu. Long press menu button -> DHW 9 room stats for a 60m2 does sound very complex! Not what I'd install from scratch, but now you have it it'd be worth seeing if you can make it work as needed. Sounds like the main thing is it calling for heat with too few actuators open. I'm controlling my ecodan via loxone and it's trivial to set it to only call for heat to the ASHP when some minimum % of rooms have a requirement for it, but with a wiring centre that doesn't generally seem supported so the easiest first step maybe to just remove the actuator from the largest living area loop, that way that is always there as a heat sink for the ASHP at least.

It maybe that they lack capacity in the cabinet that services that property too. So this is "dead man's shoes" that if another neighbour cancels their subscription you can jump in and get it. If sharing a link the main issue with VM even on their very top tier product is uplink bandwidth (and latency and jitter) and sharing a link could make that worse, depending how you do it. More of a problem for gamers and video conferencing.

14 months (original estimate was 8 months; COVID added about 4 months, the rest was the usual overoptimism)