Rob55

Holy thread revival Batman! I was just googling the exact same question and wondered if the OP or anyone else has come up with the answer yet? ?‍♂️

Construction is dense blockwork cavity walls. The house is already plastered so the only exposed clockwork that really needs parged is the ceiling void with the first floor joists. MVHR is already agreed upon. The last house is built was tested at 0.8ACH and I'm optimistic I can get close on this retrofit!

Hi Can anyone give me advice on how to airtight first floor joists which penetrate the inner leaf blockwork into cavity walls? I am wondering should I use plasterable tape, and wrap it around each joist where it punches through the wall. And then plaster all blockwork between the joists? I am currently renovating a 1980's house which I intend to go with full air tightness measures. All plasterboard is down so I have a chance to remedy all weaknesses, and the first floor joists are top of my hit list!! Thanks

I am looking at home automation for a new build and really like the Loxone stuff. Question is though, to save cost, can me and my spark give it a go on a DIY basis? I see they sell all the components online, but how hard is the system to design and configure for a complete novice? My spark doesn't have the time to research it or go on a training course, so I would have to steer him myself. I have no IT or electrical background but I am pretty good at picking things up. Or are there any other alternatives we should be looking at? I was quoted near £30k for a whole house system of another brand and I nearly fainted..

Gentlemen, thanks to your input above we have now ordered a Samsung Gen 6 ASHP (9kw). The SAP Calc for the house is 6-7kw heat loss so both my supplier and underfloor contractor both agreed that 9kw was ample in size. I hope it does a great job and doesn't cost the earth in electricity!!

Also is it possible to have mains pressure when taking a shower, or do you need a pump to work in conjunction with a hot water cylinder?

Bigger than the equivalent size of cylinder that would be used with an oil boiler

Can an ASHP supply hot water for showers and baths? Can ASHP heat the water quickly enough or do you need to have a bigger cylinder to store the water in? I also see some ASHP’s advertised with a hot water cylinder built in, surely this would be very inefficient as the cylinder and pipe work would be outside in the cold, or is there another reason for it?

it could well be, the spec sheet just says “UFH Load 16.5kW” If that is the case, any idea what size ASHP would cover it plus hot water? 141m2 downstairs and 64m2 upstairs.

My UFH says it has a heat load of 16.5kw, plus say 3kw for domestic hot water, am I wrong to assume this needs a 20kw heat source?

from some internet googling I think my original cost estimate of £7k isn’t far off the mark? Quote: The cost of an air source heat pump unit can range from £6,000 to £8,000 and will depend on the size of the property it needs to heat. On top of this is the cost of the installation and of additional works required to upgrade the distribution system. (Generally speaking installing a heat pump is not especially disruptive work, though you may want to carry out this work at the same time as other home renovations.) The running costs of an installed system will also vary depending on how much heat it needs to produce, what type of distribution system you have and the CoP of the system (see above). The cost of the electricity used to run the heat pump for a typical two-bedroom home is around £900-£1,200 per year, and up to £1,800-£2,400 for a four-bed home. This is generally cheaper than the cost of heating with electricity, oil, LPG or coal but more expensive than gas. Maintenance costs for air source heat pumps are low. They are reliable, work automatically and have a long life.

Really, I must honestly admit that on "hearsay" I thought ASHP was more like £6-7k. Will get looking into this asap, thanks for the advice

Just looked at Kingspan’s email and they have actually done an EWI calc based on only 50mm EWI (Kooltherm K5 so it’s the more dense board) and it’s bringing the U value down to 0.21. This could be a compromise that would work with my granite sills and heads!

Yes if I go EWI, I will install the insulation myself. It seems handy enough. The outside of the house will be getting thin coat render anyway, so the overall insulation cost is definitely manageable. And it seems to kill all the wall based cold bridges, leaving us to concentrate on window detailing and floor/ceiling detail. i had seen foam stone before but no experience with it, architect had a sample but said they have never used it, anyone know if it’s any good? I had Kingspan run some calculations and if I go for internal insulated plasterboard, I have no risk of interstitial condensation at 62.5mm (and even at 102.5mm) so at least that’s still a good option if I don’t go EWI.

There’s no grants over here for ASHP and we have built an eco home which is both super insulated and airtight, so oil is the cheapest way of heating. Architect projects total bill for the year to be around £250! House is 2200sqft. Even if the oil bill was £500, which I fully expect that it will be, I don’t see ASHP as having a short payback. As for water filtering I wasn’t sure on the capacity maybe a couple of IBC’s was just a throw away comment but my point was that a di vessel will leave the incoming water completely pure and remove hardness from the water. We had to do it on an industrial heating system with a couple of IBC’s and I always thought it seemed like a great idea for UFH as you don’t get a second chance if a pipe blocks up with calcium deposits after 10/20 years!

So would the consensus be that a buffer tank is needed, I already asked both my architect and plumber this question and they thought it was overkill... but to me, a boiler cycling on and off isn’t a good thing? Also, for the UFH, does anyone ever filter the water going into the system for the first time? I was thinking of buying a di vessel and getting a couple of clean IBC’s to filter the water into to prevent build up of crap inside the heating pipes..

New build house with UFH - what condensing oil boiler would you go for? It's in the garage so I presume a boiler house model of the appropriate size (70-90), but are there any other things to consider or brands to avoid?

Hi @Ferdinand This will be my forever home, so I am prepared to go the extra mile. Sorry for stupid question but what is 2G? I am thinking internal insulation will be best bang for buck, and seems like it would have the best response to heating by keeping that heat within the room. But definitely worried about shifting the dew point and causing condensation/mould within the rooms. I will definitely be putting in plenty of loft insulation, easy win in a 2 storey house, there is already a layer of wool up there and I can easily add 2 more layers of 200mm each for low cost and zero labour cost. As for the floors well that's a bit more tricky as it would require taking up the screeds and existing eps (I think it has 50mm at best) and replacing with something high density like Kingspan Kooltherm and a liquid screed in order to maintain floor heights. Added benefit would be that I could put down UFH in the process, but only after the labour costs of ripping out all the old floors. Keep the ideas coming!! Cheers Rob

Hi I have a 2 storey house of 1980's construction. Inner/outer walls are constructed of 100mm concrete blocks, and a 70mm cavity fully filled with bonded white beads. Approx u-value of 0.46 and no air tightness detailing! I plan to completely gut and renovate this house to a high standard - new windows with good thermal detailing, insulation upgrades and if possible air tightness improvements where possible. At the moment I have planning permission and am moving on to detailed construction drawings for building control, so need to make the decisions now regarding insulation. So, what to do? 52.5mm Insulated Plasterboard, approx U-value 0.22. Easy to put on, and internal walls will need re plastered anyway due to window re modelling. However, I am concerned about condensation as I have heard a few horror stories about the dew point moving within the room, and I don't know how to stop this from happening. 100mm External Wall Insulation, approx U-value 0.19. External walls will be getting re-rendered anyway, so the main cost is just the insulation and labour. But I want granite window surrounds and heads, so I don't know if they can be fitted with 100mm EWI. Can either method be used to improve air tightness? I know that there will be a lot of air weaknesses in the current construction - plug sockets, the void between floors, etc etc. Any other ideas that could be done to improve what's there? Cheers Rob