Jeremy Harris

PassivHaus has never been about having no heating, for several very good reasons, not least of which is that if you built to a "no heat input ever required" standard then the house would almost certainly need a fair bit of cooling in warm weather. We don't like the house to be warmer than about 24 deg C, and with the level of insulation and airtightness we have (similar to @PeterStarck, although not certified as a PassivHaus) we have found that cooling can be an issue at times. Over the past couple of years we've had days when the outside air temperature has been higher than we'd like the house to be, so opening windows just makes the house warmer. The choice of heating system is really down to personal preference. We have an MVHR that has a built-in air-to-air heat pump, and that has enough heating capacity to keep the house warm in winter, but I don't much like the "feel" of warm air heating, so we don't use the MVHR in heating mode, only in cooling mode in hot weather (the heat pump is reversible so will cool the air as well as heating it). We had UFH pipes cast into our passive slab as a part of the package, so we heat and cool the slab with a small ASHP. We find that the very small heat output from the UFH gives a comfortable feel that we both prefer, but that is just a personal preference. The heat input needed even in really cold weather is tiny, so the UFH never makes the floor warmer than about 23 deg C, if that. We also have heated towel rails in the bathrooms, and they have to be on a timer I've found, as otherwise they tend to make the bathrooms too warm. Local climate makes a very significant difference to the heating and cooling requirements of a house that's built to passive standards, and I found that we accidentally created a significantly warmer micro-climate around our house as we had to cut back deeply into a hillside at the bottom of a valley to get a level plot, and that's had the effect of providing a lot of shelter from the wind, so we have an air temperature around the house that's normally 1 or 2 degrees warmer than the local weather data suggests. The effect of this was to seriously screw up the PHPP over heating risk prediction, which then meant having to add external solar reflective film to help keep the sun's heat out in Spring and Autumn (we have overhanging shading to deal with the summer sun, but that doesn't work for low sun angles). The most important factor when looking at construction methods for a low energy house is, IMHO, making sure that the wall and roof construction method provides a high decrement delay, so that the house has a long thermal time constant. Once the decrement delay exceeds the time that the sun is likely to shine on a surface, say 6 to 8 hours, then the risk that radiant heat will be conducted through the walls and roof to the interior reduces a great deal. Decrement delay is a function of both the thermal resistance and the heat capacity of the structure. Having a low U value structure with a low heat capacity will give a short decrement delay, so it's important to consider this carefully. Finally, wind has a pretty large impact on heat loss, and this becomes more noticeable as you decrease the overall heating requirement, to the point where wind speed around the house may be as important as the air temperature in determining the heat input required during the heating season.

That's pretty much what I have. I had the ceiling boarded, with 200mm of rockwool between the ceiling joists, which are 220mm deep, as they are boarded out on top to give a small loft storage space. I have a cold roof above this, albeit with a totally useless layer of multifoil insulation stapled across under the rafters (all that's useful for is reflecting light better from the loft lights). I have ventilation under the eaves and at the ridge, so the space behind the slates is pretty well ventilated.

I'm pretty sure I've mentioned this before, but the only thing that was thoroughly checked during our final completion inspection was the access route from the parking area, up the ramp into the utility room and the access to the WC that leads off that. The outward opening door and wheelchair access spaces were measured to check compliance. I reckon that this check was took up around 1/3rd of the time spent on the whole completion inspection.

Damned good idea! That may well work a treat, and have the added advantage of the doors not projecting out as far on the rare occasions that they are opened.

Sadly I have benches fitted on both walls, so have no room for anything that slides inside. The "garage" is really a boat building workshop, 6.1m long and 4.1m wide, hence all the insulation and internal creature comforts (I've even fitted aircon...). I've been looking around to try and find anyone that can make a pair of 1.5m wide timber doors, that I could then add some internal insulation to, but have had no luck so far.

External Wall Insulation. You build a single skin structural wall then clad it with insulation on the outside and either clad or render over the insulation to provide a rain screen.

A 7 kW electric shower, with an incoming cold water temperature of 8 deg C, and a shower temperature of 38 deg C, will only give a flow rate of 3.35 litres per minute, so your guess of your shower having a 3 times greater flow rate, @ProDave, is pretty much spot on, I think! Electric shower flow rates really are pretty poor, IMHO, although having said that we managed with a 10 kW one for a few years (that would give a flow rate of around 4.785 litres per minute). The problem is that once you've experienced a shower that flows at around 10 litres per minute or more it's hard to switch back to one with 1/3rd of the flow rate.

I have a feeling it may be to do with the way that the internal flap is oriented. It perhaps doesn't like to see flow towards it's non-hinged edge? I fitted motorised ball valves, as they seemed to me to be a better solution, not least because they don't consume any power in either position.

Building regs require a minimum clear opening width for the entrance level WC of 750mm. Unless a 762mm door can be made to open right back, and only have thin stops, I doubt that you can make it comply, I'm afraid.

Good point, @ProDave I'd forgotten about the 18 kWh of initial charging for the two Sunamps. Looks like you're DHW demand may well be close to my estimate for ours, at around 3.5 kWh per shower. Showers dominate DHW for us, as there's barely any other DHW use, other than hand washing etc, which might be around 1 kWh/day at most, I suspect.

An average shower probably uses around 100 litres of water at around 38 deg C. I measured the shower at our old house to come up with this number, and found that our shower delivered around 10 litres/minute at that temperature, and I take 7 or 8 minutes to shower, my wife takes 10 to 12 minutes, so 10 minutes seemed a reasonable estimate. With incoming mains cold water at 8 deg C (may be lower than this in some areas) the temperature increase required is 30 deg C. The energy needed to raise 100 litres of water by 30 deg C is 3.48 kWh. A single Sunamp UniQ 9 fully charged should be able to deliver around 2.58 to 3 one hundred litre showers with a 30 deg C temperature uplift. Two should be able to deliver about double that. Using 34 kWh in 24 hours on hot water alone sounds extremely high to me. Is there is some sort of thermo syphon on the DHW side that's been accidentally created and is increasing the heat loss dramatically, perhaps? Edited: Just realised that I think you're running the UFH off the Sunamps, too. The slab can hold a lot of heat, so if the UFH has only just been turned on then it's quite possible that the slab may have soaked up quite a few kWh. 34 kWh still sounds very high, though, especially as the UFH was only on for a couple of hours.

My garage/workshop has 150mm of rockwool in the walls and 200mm in the ceiling and it doesn't get too cold in there, but as @ProDave says, the door (an "insulated" roller) is just hopeless. My main problem is that the door faces South and gets pretty hot, even in winter, and acts like a giant radiator that quickly over heats the garage. I'm seriously thinking of replacing the roller door with some insulated timber garage doors, but they would need to be hinged and open outwards, as I don't have any room inside for anything else, and the door opening is 3m wide, which I think is too wide for just a pair of doors.

The efficiency claims for some of the snake oil electric heater adverts really should be regulated, as they are grossly misleading. The losses for a Sunamp UniQ 9 are around 0.7 kWh/24hrs, so you can estimate how much sensible heat you can get out for any given input, depending on your usage. I would guess that for many households the hot water usage per 24 hours may well only be around 1% to 2% of the time (24 mins to 48 mins hot water draw off time per 24 hours), so just assuming a loss of around 0.7 kWh per day should be close enough. That gives an estimate of efficiency, in terms of energy in to energy out per 24 hours of around 92% to 93% if pretty much all the energy is used each day, so perhaps a bit better than a good battery storage system (I think the best battery storage solutions are currently around 85% round trip efficiency, but they are getting a bit better, I believe). Realistically, most people may not use all the stored energy each day, so efficiency will drop significantly as usage drops, because the losses are near-constant.

I'm always a bit wary about clauses like this, primarily because insurers are extremely adept at finding a way out of paying out, and I'd lay money that they would try not to pay out in the case of a normal buildings/contents policy being used to cover a partially built self-build. When we were quoted a ludicrous premium to extend our self-build insurance (which came via the infamous Buildstore) I shopped around and was advised by a helpful broker that we really needed to be completely upfront about the house not being lived in, just being worked on most days. IIRC, I ended up paying something like £300 for a year's premium on a custom policy that was based on a renovation insurance policy. There were several specific things we made sure were clear, including not living in the house, having the heating working, ensuring the water was turned off when no one was at the property, etc, and there were limits on things like water damage from leaking plumbing which I agreed to.

Another problem with ordinary buildings and contents insurance is that there is often a clause stating that you have to be resident at the address and spend no more than a given number of nights away from it during the cover period. I was surprised at how limiting some policies were; 30 nights away as a limit isn't unusual.

The problem for us in doing that is that the slab carries on giving out heat for many hours after the UFH turns off. Any sort of individual room control just doesn't work well, due to the long thermal time constant. Boosting the MVHR tends to get rid of heat reasonably well, as the heat recovery efficiency drops a fair bit on boost and we have three extracts from the kitchen/dining, utility and ground floor WC all pulling air through from the entrance all into the kitchen/dining room. When it's not too hot outside, then just opening a window in the kitchen works OK; it just unbalances the MVHR a lot and pulls cooler air in from outside.

The permanent line is internally fused at 3 A. The heating element switched line runs a 2.8 kW at 230 VAC heating element, so around 13 A at 240 VAC. I doubt that the permanent line current ever gets over around 100 mA, despite being fused at 3 A, as all it runs is the 6 W nominal control circuitry plus the relay that switches the heater on and off. Two Sunamps charging at the same time will draw around 26 A or so, well within the rating for 4mm2 T&E, clipped direct, and just about OK for 2.5mm2, although too damned close to be used in practice.

Sadly, polyester resin and even the slightest trace of moisture is a recipe for failure of the GRP. The "topcoat" should be a waxed gelcoat, and will be equally susceptible to poor curing from any moisture inhibiting the cure of the underlying resin. The gelcoat with the added wax tends to seal in moisture during the early stages of the curing process, as the added wax is there to float to the surface and exclude the inhibiting effect of moisture in the air during the cure. This has the unfortunate effect of trapping any moisture that's already underneath the GRP, and this moisture will then end up staying in the partially cured laminating resin in the GRP itself. Any over-coat won't fix the problem, and will be, at best, a stop-gap repair. I'm near-certain that you will find that the GRP isn't bonded to the substrate. As you almost certainly can't replace the GRP at this time of the year, because of the weather, I'd be inclined to just try and do a temporary fix with a bitumen-based repair solution. This will preclude you putting anything permanent on top of the failing GRP, but should get you through the winter without costing an arm and a leg.

Yes, only one fire escape window is needed in any room that doesn't connect to a circulation space that has an external door, or is above ground floor level. One issue is appearance, though. A fixed light next to an opening light can look a bit odd from outside, but if the window is big enough to be divided into three, then a centre opening light can look OK. There are three windows in our build that I wish now I'd made fixed, as they are never opened.

I've not found any problems with using a hall mounted thermostat at all. This might be because it's virtually in the centre of the ground floor, so opening outside doors some distance away has virtually no effect (I've never seen the under floor heating or cooling come on from just opening a door). I do have our air cooling thermostat mounted on the landing on the first floor. I moved it up there because the upstairs was getting to be around 1 or 2 degrees warmer than downstairs in very hot weather, so there is an advantage in having the air cooling triggered a bit earlier, especially as it's neither very powerful and because it's the only means of cooling the upstairs when the outside air temperature is high. I think a great deal depends on the layout of the house, and whether or not a thermostat is placed somewhere where it might be susceptible to a draft when a door or window is opened. Having a wall thermostat near the centre of the house, in a location well shielded from drafts, seems to work very well for us, and may well be a good general solution for those using off-the-shelf controls.

Yes, I believe it does, and may also need PP as well, I think.

We bought a house in 1997 that had a DIY loft conversion that had been used as a children's bedroom from the mid-1960's to the mid 1970's. That definitely didn't comply with building regs in any way, shape or form, but the vendor admitted this, said her late husband had done the work with no approval, planning etc and she had the (bodged) space saver stairs removed and adjusted the price down to reflect that the house then had one less bedroom. Our surveyor noted that the "loft" was decorated as a bedroom, complete with a (non-fire regs compliant) dormer window, but advised that it wasn't a habitable room due to the lack of access stairs. Our building society had no problem with this, and it wasn't a problem when we came to sell, either. I think that had it been a habitable room that definitely didn't comply with building regs, or had no evidence of compliance with building regs, then there would be a major problem with the majority of lenders, as well as insurers.

I've recently bought an Odroid HC1 plus a 2Tb HDD, which one day I'm going to get around to setting up as a replacement for my existing OwnCloud home file server (which runs on a RPi3). My primary reason for doing this is just to improve the file server speed a bit and be able to use an off-the-shelf SATA HDD (or SSD, but big ones are still too pricey for my budget). Having a SATA or mSATA native port on the next generation of Raspberry Pi would be the one thing that I'd like to see. Running everything through an onboard USB 2.0 hub, as the RPi does at the moment, isn't ideal, IMHO. You can make things work over USB 2.0, but it seems to be a sub-optimal hardware solution to me.

The only rules that apply as far as fixed lights are concerned are the means of escape from fire from habitable rooms that are not directly connected to access to an external door. In general, any room that doesn't have a door leading directly to a circulation space that has an outside door, plus all upper floor rooms, need an opening window that meets the escape from fire part of the regs (lower edge not more than 1100mm above the floor, IIRC, plus minimum dimensions that are given in the regs). If trickle ventilation is required, then this is fitted to the outer frame usually, so can be fitted to fixed or opening lights I believe. For some reason, there isn't a massive saving in cost for fixed lights over opening ones. No idea why, but I had both options priced and the saving was pretty small.

The problem with the "rent a roof" schemes was that they impacted negatively on property prices. Buyers weren't keen to buy a house where they weren't able to change or remove the solar panels, as they remained the property of the "rent a roof" company. IIRC, the penalty charges for having the panels removed were also pretty punitive. Some of these installations date back to when the FIT scheme ran for 25 years, rather than the 20 years it runs for now (until it's closed to new applications next year).