Iceverge

Get a farmer to chuck a few sheep or cattle in there for a day. You won't know yourself.

From my reading the only way to have a permanent good quality of internal air is some kind of continuously operating mechanical ventilation so it's worth pursuing. If it was me I'd look at the price of a whole house continuous extract system as you may get most of the benefits of MVHR as you may have poor airtightness. That vent axia unit looks fine but perhaps a little small. Rated only to 40m2. A larger unit running less hard will be quieter.

Have a good nosey at mass housing developments near you. The build method they are using is likely to be the cheapest and well known to local trades. Copy everything from the foundation to the windows to the roof covering and you won't go far wrong. Avoid buying strange and exotic materials that can't be picked up from your builders merchants. The ability to pick up a few more joists from if you break one or drop back a few unused roof tiles for a refund will save money and heaps of time.

Yup, all be it 100 times larger! @TerryE has cracked it I think, although the approach of Jeremy Harris with a simple thermostat is probably good enough.

Start on the drawing board. Keep the design square and as small as practicable. Most semi detached houses are less than 100m2 and people survive just fine. We ended up at about 180m2 but 150m2 wouldn't have made much difference. I spent a lot of time designing to make it super simple to install services etc. The trouble was that the benefit of this all seemed to be soaked up by trades finishing the job by Thursday and taking Friday off. There was no reduction in price as people seem to quote by looking at the footprint area and multiplying it by a figure. Mind you it's our builder who probably missed out here as we were a fixed price contract.

Ah, I didn't consider the hotspots. I suspect electricity will never get cheaper or more expensive than the majority can afford to pay.

I know it rules out the possibility of using an ASHP but has anyone embedded resistive wire heating in the slab (not on top of)? You could have the same delayed energy release of a water heated slab with no moving parts and no water.

I have and enjoyed it too! We're about to move in so I don't think it's a runner as we'd have to take up all the floors bathware, stairs etc. We have 200mm EPS under the floor and strip foundations not unlike the denby dale version. There is a thermal bridge there but I've modelled it and accounted for it in PHPP and increased the insulation elsewhere. For our build it was about €5000 cheaper to take this approach although that might have changed in the last 2 years as I've noticed a developer near us using the KORE insulated raft on a development. +1 on the rigorous oversight needed but I was more hoping @dnoble could provide verification of both the software process and the build integrity with his electricity readings for the heating component. I aimed to keep the house as "dry" as possible for long term reliability (100 years +)and with that in mind we have no conventional heating either. Just an UVC for hot water. I was unconvinced by the Sunamp's benefits given the price uplift. We may well switch in the future. The unoccupied house is currently sitting at 17.8 deg with an overnight topup from a 2kw fan heater ( €1.28/day) and capital cost was €0 as a friend was throwing it out! (BTW I returned my Lidl model mentioned in another thread) We have left provision to install an Air to Air split unit if out heating demand requires it. About €1500 with a COP of 6. With this in mind I couldn't make the sums work for an ASHP either. Payback was in excess of 25 years. Much like @dnoble I hope to wait and see what the first full heating season works out as (winter 2021/22) and redo my sums then. BTW a neighbour of ours has a passive house built in 2010 and has never needed to install any heating. SW Ireland gets less temperature extreme than England. @dnoble Thats a great result. Working backwards for 125 days @ 21kwh/day for heating = 2625kwh/annum for 240m2 is 10.93kwh/m2/annum. Better than passivhaus.

So roughly: Built in is £105m2 + labour. On Roof is £89/m2 + slates/tiles + labour. The difference sounds marginal.

Well done. I’m beginning to think this is an excellent method of heating a passive house. It is relatively cheap to install, zero maintenance and super simple so shouldn’t break down. The main one is though the ability to use all that slab concrete as a giant storage heater. If i suggest to our builder at this stage we dig up the slab to install pipes I suspect the only way he’ll agree is if he can bury me under it! Out of interest have you any idea how much electricity you’re using compared to what phpp predicted?

This is what I was thinking of. I suspect you'd be unlucky to have it leak anytime in the near future but there are more areas of vulnerability than built on panels with a full roof covering below. They'll run more efficiently with ventilation behind and be easier to upgrade in future. Arguably less handsome however. I don't know about the total installation cost comparison

I'm a bit sceptical of build in panels. Will replacement parts of the same size be in available in 30 years or sooner if the panels fail? The more holes and fiddling and flashing you do with the roof the more likely it is to leak. Maybe not tomorrow but some day. With that in mind our PV is going on the garage and there's not a single penetration or hole in our hip roof. No lead no joints no nothing. Paranoid maybe!!

Avoid making any holes if at all possible. Service cavities in all external walls and ceilings. Duct in services through the slab and backfill with fine sand around cables pipes etc. MVHR ducts were solid ducts and taped/ airtight painted to the walls inside and out. For the cables to the attic I drilled holes for each wire in a piece of ply and placed sealant around each hole.

The design looks lovely I really like the style. I think £300k is tight given the complexity of the building. You could do it for this if you’re content to live in a building site for literally years on end. We’re 17 months into our build and it’s really dragging on. I can’t imagine the stress if we hadn’t aimed to build a €220k house within our €300k mortgage. (I think we’ll end up at about €280k by the time everything is actually done) You have lots of unusual angles and junctions and the surface area of the house is quite large for the floor area. In short unless you buy excellent windows, put in lots of extra insulation and are very particular with the workmanship you might end up with an expensive house to heat. In terms of size I certainly wouldn’t make it larger, possibly smaller and simplify the shape of the building. Reduce the external wall surface area and all the hall space and other dead space. If grandkids do arrive simple bribery will certainly suffice! Good luck!

Don't forget you can use different thicknesses depending on how much space you need in each room. battening at 90deg to the rafters makes it easy to run wiring and if you insulation inbetween it cuts down on thermal bridging of the rafters. For my money I'd use 50x50mm battens with 50mm mineral wool inbetween.

I think you'll be fine.

Yeah, maybe you're right. Scraping through the SAP by hook or by crook isn't a great start.

No heating at all upstairs. In a new house you won't need it.

5 years is a long time and a lot could change by then. In terms of energy saving the lowest hanging fruits to improve on building regs are. 1.Triple Glazing 2. MVHR 3. Airtightness Added insulation is only an incremental gain in comparison. You could probably ditch the rads upstairs too in all but the bathrooms.

The building control in Ireland is done by the design professional e.g. Architect/engineer. The process is less than rigorous and the hazards of incorrectly installed UVC's are not widely understood. I spoke to the manufacturer and he's OK with the expansion arrangement however I'll at least get them to take the handle off it. He was ok with the over temp line dimensions and length too but I can't see any reason not to redo it as per MIs when the tundish is being fitted.

Thanks @PeterW We are in Ireland and believe it or not Bregs are silent on this. I can imagine that'll only change when there's an accident. 1. The discharge pipework into the main wastewater pipework. Will it need a trap to prevent smells or is this not allowed? 2. Understood 3. Would thermostatic mixers for the bath count? I want to have the option of storing water at the max tank temp anyway so I'll insist if only to keep the basins safe. 4. Understood. I'll get him to insulate.

Hi All, The plumbers put in our UVC cylinder yesterday. I have raised a few things I spotted with the main contractor and he was getting in contact with the plumber. Could those of you with more experienced eyes please have a glance at my picture and let me know anything else that needs to be rectified. What I've noticed/questioned. 1. There is no tundish fitted and the over temp valve discharges via some 16mm pipework over a long distance to a hidden pipe into the main waste water system. 2. Does the tank require an overpressure valve on the cold feed? There is one on the cold main entering the house. 3. Does the tank require a thermostatic mixing valve? 4. Is it safe to have a switchable valve on the expansion vessel? Thanks in advance.

Be cautious of thermal stores as well combining your DHW and heating. You'll inevitably end up with complex, expensive system and the prospect of the UFH stealing all your bathwater. Using water to store heat isn't very efficient as it typically needs to be done at high temperatures and even the most pricey cylinders leak lots of energy. Your heating requirement also seems high. Is the house old and poorly insulated/draft-proofed/ventilated? This is your first point of call. I'd stick with an UVC for DHW. The larger the better, as a large cylinder will lose less energy than a smaller one for a given amount of energy stored. If you need to "bank" cheap overnight heat just dump it into the slab. With a slab thickness of 100mm you'll have about 20,000kg of concrete. This will store 5.5 Kwh for every degree you raise it's temperature. If you had a large 500L buffer tank you'd have to raise it's temperature by 10deg to get the same effect. This is dependant on decent insulation below your floor however. Search @TerryE blog to have a look as how to achieve this.

They were 150mm diameter acoustic silencers from BPC ventilation, 500mm long. I would recommend them for build quality and ease of installation but I can't comment on their efficacy as to sound attenuation, they seem to be working. Yes perforated inside as best I remember. They're pretty cheap also. https://www.bpcventilation.com/quiet-vent-semi-flexible-silencer-range I'm yet to see any evidence of it ever happening so as of yet I'm unconvinced it's anything more than a theoretical issue. If I was to build again I'd consider not bothering with a specialised terminal. One thing that I took some trouble over was fashioning the insulated ducting to run from the MVHR to the exterior. As you can see I taped the joints with airtightness tape to back up the internal seals. If you put your hands against these joins you can feel it's colder than the rest. I'm going to wrap more insulation over it when the builder is finished filling the holes in the plasterboard. I'd hate to see ducting being left insulated. It'd be a huge heat sink in a well insulated house.

For the look you hope to achieve I think you'll be disappointed if you don't change the roof covering too and while you're up there it'd be a shame not to re-insulate Could you post a dimentioned drawing of the facade along with a picture perpendicular to the front and I can try some ideas if I have the spare time.