Has anyone looked into the incremental improvements in house insulation from RT 2005 onwards.
We’re considering buying a house built in 2007. It probably had an oil boiler initially and now has a pompe de chaleur with an energy rating B. Of course that is telling me the house is cheaper to heat now but nothing about how well it remains cool in a heatwave. As far as I know heat pump powered underfloor heating cannot be used to cool.
It can. We’ve a gas/water geothermal heat pump and were given the option of using it as air-con in summer, as well as to heat the pool. As we’d done the insulation ourselves way beyond the normes in 2007 we opted to do without on the principle that it might prolong the life of the heat pump to have a ‘rest’ in summer.
Apart from floor, attic and wall insulation, the biggest single factor in keeping the place warm in winter and cool in summer was using multicouche foil insulation over the whole roof, under the battens and tiles. Back then, the maximum available was 17 layers. I believe it’s increased since then. The house stays at a comfortable 24C max when it’s 40C+ outside. HTH
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I can echo the same with the insulation in the roof, despite multicouche not being accepted by the authorities (quite stupidly IMO) it causes a room space seal from drafts and heat infiltration and backed up by 200mm of rockwool was transformative to our property.
Some heat pumps are reversible so can cool a room in summer.
The key to low cost running of heat pumps is radiator/emitter sizing according to a heat loss calculation and using weather compensation to adjust how hard the system works based on an outdoor sensor, same with a condensing gas boiler, the lower the flow temerature the better for your electricity bills whilst maintaing a comfortable temperature indoors. Sadly when you hear horror stories its usually through a bad install, smaller pumps are better than oversized.
Its your call of course but running the pump even at a low level occasionally is better for the pump than long periods of innactivity.
It’s not switched off because it also powers the hot water system twice a day (on cheap rate) 
Is multicouche not accepted in UK or has it been banned in France?
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Multicouche was a bit oversold, they made big claims about it being equivalent to xx mm of glassfibre/rockwool/foam etc. When tested by several research institutes on usually “hot box” testing it did not pass the eqivalence tests. That said it still does a bloody good job installed correctly. The UK has no problem with it rightly or wrongly stating its effectivenesd. France ignores it from the view of the diagnostics test which is daft as they manufacture so much of it but thats France’s short sighted overview. Used corectly and as you state and as I atest to, it reflects the high heat of summer really well and retains heat in winter very well purely by its reflective properties. Having read the reports prior to my install I backed up the multicouche with rockwool at 200mm (150mm was not available) and it has performed amazingly well. As with all wool types of insulation there is air movement so some heat gain/heat loss is expected, using a membrane to seal that heat gain/heat loss such as multicouche improves things vastly despite what some diagnostic nonsense may say.
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I used 21 layer multicouche as a temporary solution for our attic ceilings as it was a cheap and easy DIY fix. Currently its 8c outside and 16c in the unheated attic. I believe that 20+ layer multicouche has an R value of 4+.
Eventually I plan to remove the multicouche, install 100 or 120mm glass wool panels, re-install the multicouche below the glass wool panels and then fix plasterboard below that.
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I fitted mine to other way around, multicouche under the tiles (with air space) then 200mm of rockwool. The main idea was keeping it cooler in summer by reflecting heat away. Either is fine. I have long since lost the R values of real world tests, if I can find it on an old pc drive I put it on here.
What is the expected lifetime of air/water heat pumps? The house we are interested in is 17 years old. I only know (so far) there are two fan units and the make is Panasonic. Checking on service history. Should they be serviced annually? What work would be carried out?
Always tricky to say but probably coming to the end of their life, also spare parts availability for units that old? New units have moved forward quite a lot technically, old units were often on/off whereas new units are variable speed compressors and fans so can modulate performance saving you money and less wear on the internal parts. Old units can often contain refrigerents now banned so consider a new unit in the not too distant future.
Servicing wise, pollen build up etc on the external radiator requires cleaning as needed. Checking performance is now often done via the software.
I’ve looked into this a bit since I was in a similar situation with a house built around that time. From what I’ve gathered, houses built after RT 2005 tend to have better insulation, better airtightness, and generally do a good job keeping energy costs down. I wouldn’t rely on the heat pump for cooling, though—underfloor heating won’t help with that. In terms of staying cool during a heatwave, if the house is well-insulated, it should naturally stay a bit cooler, but if you’re worried, you could always look into adding a small AC unit or heat recovery system to help balance things out. Definitely worth checking the insulation yourself to get a clearer picture.
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Thank you
A reversable heat pump is an AC unit when working the other way. Heat moves to cold so if the floor is cooler the room will cool. Ok it wont blow cool air around but a fan core unit could probably be fitted to the unit by plumbing in, its certainly something I am looking into and I will speak to my HVAC guy.
I have a system like that and have/am very pleased with it all. Engie even sent me an email congratulating me on using less energy than last year, this morning and my running costs for both the airpump as a water heater and the reversable heating/air con are far less than I ever thought it would be. Service is yearly and now I have to pay as my system is just over the two years.
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Someone did a spread sheet and made it fit into 7 catagories