Iceverge

From the inside out. Skim, 20*70mm battens for service cavity. 50mm PIR on top of the studs. Taped and foamed. 44x95mm studs infilled with mineral wool. OSB sheathing. Breather membrane.

Its the air temperature in the train at 23deg. Everything else will be colder so your bodies conduction and radiation losses will be greater than in summer.

For my 2p worth I was thinking about 50mm PIR Inboard of the studs with mineral wool in between.

If you are concerned about the cellulose how do you propose to check non destructively? Is it worth the effort?

You could jump to 50mm PIR on the wall without services or whatever you can fit. The 400cc studs really have a hit on the performance of the wall at that thickness, the calculator underestimates the true % of timber too. I would foam the boards and tape them with foil tape. Tape them to the windows, doors, floor and ceiling and you'll have a good airtightness layer too.

One of the last two options would be my choice.

I'll do a mock up shortly. But I would counter the idea that PIR between the studs is the way forward. Too dear, too much waste, to awkward to fit. Timber and PIR will expand and shrink differently and the boards will come loose.

Ah, I see the confusion. The cheap quartz heater I installed is the victor.

Right the results are in. Success (I think!) Following on from @Gone Wests thread on comfort. I think I'm onto a winner. PROs: Super cheap. €31 from screwfix. They are simple to operate, pull string operated. Settings "1" "2" and "OFF". I hate pointlessly complicated stuff. They pretty instantly heat your skin, pull chord, squeeze pimple in mirror, admire reflection of naked body (it's as good as it gets, tomorrow you will be fatter and wrinklier) and "Kablam" there's the lovely heat. I can run the shower slightly colder trading off the energy used. Baths are comfortable for longer. Dry install, no chance of leaks. 20deg bathroom feels comfortable even in the nip. No need to spend too much on space heating or preheat the bathroom. CONs: Cheap construction ( surprise surprise!) Pointless as a space heater, they just heat a layer of air by the roof if left on. 1.2kW of direct electric is expensive if someone forgets to turn it off. It looks crap. Not as radiative as a proper patio heater, more heat is lost to convection (I think) than a halogen one. Not completely sure of this but I'm suspicious. It smells a bit iffy initially, maybe a factory coating burning off or something. If you were concerned maybe something like this would be more stylish and could parabolically beam the heat at you better. Then add a 12 minute push timer. Overall I would endorse this. Simple cheap and effective.

@Gone West Original question. Comfort I think is simply the temperature we feel on our skin. Nothing really to do with U-Values really. Hence we like the sun on our face, hate cold tiles on our feet, like sitting on a radiator (briefly!) and hate a breeze when getting out of the shower as the evaporative heat losses of the water really cool our skin. For a comfort we need to manage 3 things, the old faithful trio Convection Conduction and Radiation. Convection or Drafts. Solved by airtightness and eliminating different internal temperatures that cause convection currents. Insulate cold surfaces similarly. Slow and steady heating is better then intermittent blasts, heating all the rooms equally is better than just one or two. This may not always be possible or economical. Conduction. Getting rid of cold things you touch or replace them with materials of lower thermal conductivity. Tiles for example are worse than Lino. Fit UFH. Wear slippers. Keep humidity under control, a damper carpet feels colder. Radiation. Keep you skin covered, even a light shirt will reduce the amount of energy you "shine" away. Cover windows and cold walls with curtains to reduce the amount of energy they soak up through radiation. Fit 3G windows and add insulation to cold surfaces. Add an IR heater to bathrooms to heat your skin directly after a shower. In short I think you should insulate the wall but only after tacking the airtightness and ventilation of the house first. Then you can then decide on your preferred build up based on (but not limited to): Cost Risks of low permeability materials and poor workmanship Contribution to airtightness Mitigation of thermal bridges Floor space loss Ease of construction

Almost never the case though assuming the house is habited. The MEV unit I installed in my parents completely uninsulated house has had a really positive effect on the comfort. Everything is dryer. Also the mould is gone from under the stairs.

To quote myself, this needs more digging as it's the root of most debate here I think. Every material has a different permeability. Something like aluminium foil over PIR has a very low vapour permeability, practically impervious for the purpose of building (as long as there's no holes!) A fabric wall hung drape is very permeable, almost all the vapour gets through. Gypsum plaster, Cement plaster, Lime plaster, Woodfiber, EPS, OSB, plywood, are all somewhere in the middle. Now lets move to the real world. Every house is different with different occupants, different heating habits, different standards of construction. Each house goes through daily, weekly and annual cycles of accumulating and loosing moisture in the structure via vapour. What we are aiming for is to make sure that the walls can dry out on average faster than they are being wetted. This is a case by case basis for every house. A house with poor airtightness and IWI will see lots of damp air make it's way into the walls and condensate there. However if it can dry outwards in the long term no great damage will be done. However if it's drying is restricted by say cement external render, the moisture will build up and there's trouble. Similarly a house with terrible airtightness but a cosy layer of continuous EWI could survive with terrible ventilation and airtightness as the wall would always be too warm to condensate the vapour. ( It wouldn't be healthy or comfortable through) Some forum examples here to discuss. @jayc89 has done I suspect a pucker job of their house, they PIR is taped and foamed diligently and all thermal bridges are taken care of from the inside out. Then there's proper internal ventilation and heating. Outside is properly pointed (and maybe brick creamed?) Not lightly to see any issues. Perhaps so good that if there had been external render then that might have even been ok as there was so little moisture getting into the wall initially. Good airtightness to prevent vapour reaching the joist ends would be my only concern. Suppose a typical builder had under taken the same issue, badly applied insulated plasterboard, air gaps and thermal bridges galore, noisy bathroom fans that would never be used. The same wall would probably ended up sodden for most of the year. @Roger440 maybe had some issues, maybe from a high water table pushing water up through the walls. The low permeability cement render was enough to cause moisture to build up faster than it could dry, hence problems. Reapplying lime render with its greater vapour permeability instead was enough to tip the balance in favour of more drying than wetting and - hey presto, problem solved. Maybe a dehumidifier in the room, or a fire or a French drain would have had the same benefit. Hard to say or maybe they were not practically possible. @Gone West Peter your first house had no internal "vapour control layer". Just plasterboard over open cell spray foam. As this is a relatively permeable material, one could have worried that the backside of the colder OSB sheathing ( which was less permeable) may have accumulated moisture. However your airtightness was so good (<0.6ACH) that no air leaks got to take internal humid air to the sheathing. This approach is very acceptable in the US but not so much here. @IanR I know specced a foil backed plasterboard for his house with it's external airtightness layer as vapour control measure. However I don't think this was needed as the superb airtightness (0.11ACH I think, hurray for cellulose!!) would never allow enough vapour to escape into the walls to be a problem. Similarly the MDF sheathing with it's high vapour permeability could probably have been replaced with OSB or something cheaper. ( It does help thermal bridging in his case thought.) A mate of mine built a house recently from Hempcrete blocks, TF with hemp batts insulation, more hemp blocks and lime render both sides. There's a single MVHR unit inside but I'm unsure as to the level of airtightness. The house will ok with diligent occupants. However if there's under ventilation and under heating at any stage I would worry about the moisture content in the walls caused by air leaks despite them being of a very high vapour permeability. @Gone West back to (some of) your original problem. You simply need to establish can your walls dry faster than they can accumulate moisture. Very important in this case as the colder wall will be condense vapour more readily. If you can absolutely bullet proof an internal PIR install, with no chance of air leaking via gaps, or sockets, or by the walls or ceiling and you can completely eliminate thermal bridges then I would be happy to do it. The wall will still dry (slowly) via the cement render externally but so long as it's not getting vapour from the inside it'll be ok. As an added complication, insulation giving higher internal temperatures makes the air more vapour laden, so unless you're really on top of ventilation as well it'll increase the risk further. Maybe if you're less sure of the ability to seal the PIR completely use an internal soft backed woodfiber layer with lime render. It can still readily dry inwards and airtightness isn't so vital. From a practical point of view I'm far more in favour of flexible IWI like wool batts or sprayfoam. Then at least if you get a puncture the risk is very localised to one spot. Puncture a PIR sheet or insulated plasterboard poorly foamed in, and you could expose a whole wall to internal vapour via air leaks. If you really want to be sure, EWI is almost completely fool proof from a moisture risk position as the whole structure is above the dew point. TLDR: Anything can work so long as it can dry faster than it gets wet.

Back to the point. One of those Scottish heritage studies measured the in situ U-Values of old stone and lime walls. (I think I linked it in one of @saveasteadings earliest threads). The U-Value correlated with the moisture content in the wall. Damp Wall = Bad U-Value. More importantly moisture in a structure that wasn't designed to be damp causes decay, through mould, fungus, frost action and physical water erosion. My understanding of the issue is as follows. This moisture gets into walls because of: A. Bulk water ingress. Solved by (but not limited to) Unblocking drains and gutters Repointing externally Adding roof overhangs/flashings External brick creams, French drains to lower the local water table. Fixing leaking pipes and showers enclosures. Water proof external render or paint B. Condensation from humid internal air. Solved by (but not limited to) Managing internal humidity with adequate heating and ventilation. Entirely blocking air paths through the wall to prevent air "carrying" moisture to a part of the wall below the dew point. Keeping the entire structure above the dew point. Normally with insulation, thermal Bridges must be managed!!!! Now that's all fine in theory, but unless you build your house in a laboratory that's impossible to achieve. In any case, there'll be some construction moisture in the walls anyway. You need to allow your wall to dry. To deal with this you need to the moisture to leave the wall via evaporation. This can be achieved by (but not limited to) Keeping the wall warm through heating, limiting IWI or fitting EWI. Keeping internal humidity low. Not trapping moisture between materials of too low vapour permeability. (This is nuanced, more later....) Alternatively for some construction types moisture is acceptable (e.g. foundations) but you'll need to build it out of permanently moisture tolerant materials like concrete, stainless steel and plastic.

Definitions. Thermal Mass: Sales term used by concrete salesmen to dupe customers with poor scientific understanding. Breathability: Sales term used to confuse customers who want "eco" products or have old houses.

It sounds like an issue with the external render allowing bulk water through. Maybe some pictures would help us diagnose. Get it patched up. Be particularly observant about and cracks around windows and at the top of the wall.

Sorry I was a bit off with my calcs. 10mm of a thermal conductivity of 0.0195W/mK will give a U value of 1.95W/m2K. for £150. 18mm of Rockwool with a thermal conductivity of 0.035W/mK will also give you a U value of 1.95W/m2K. You can't buy 18mm though so if you can fit 25mm of rockwool it'll be a U Value of 1.4W/m2K for a cost of £3.

50mm PIR. 11mm ply ripped into strips for service cavity battens. 11mm OSB Finish.

Are you sure the heat pump is working and it's not just operating on the back up immersion? Is it cycling a lot?

Digging in these numbers a little. 200kWh sounds like your monthly DHW usage so 2400kWh/annum. At a COP of 3 that's 7200kWh/year. Quite a bit I'd have said. What temperature do you heat it to and do you have 5 occupants who enjoy a bath daily? Anyway taking that out of the equation I make the heating load about 10000kWh for the year. If the 16000kWh is correct then the you will only be achieving a COP of 1.6, which isn't great. Do you have any gas bills pre GSHP to compare or oil usage? How hot is your flow temp to the rad? How hot is the house kept?

Preach. Poor airtighess causes almost all condensation issues with air leaks actively transporting damp air to colder surfaces. Almost none happens through diffusion through permeable materials. If you can assure a excellent airtighess layer somewhere then I wouldn't worry about condensation. @WGL how exactly are you planning on sticking the EPS to the underside of the joists?

That kind of cash would make it a much more attractive idea. At a rough guess for a 180m2 house. High quality MVHR unit ex ducting and manifolds. £2.5k ESHP cylinder for DHW £2500k A2A unit for space cooling+heating. £1000. A bit of money saved because of avoiding a few different installers. Catching up on an old thread earlier I saw a Genvex unit had only failed after 25 years. It could persuade me for a passivhaus.

As far as I know the specific circuits for TOU tarrifs are gone in Ireland. Not sure about the UK. The whole house just goes to cheap leccy at certain times. A blanking plate over a prewired back box wouldn't be too intrusive in my mind.

Its pretty bamboozling. I got a bit miffed with all the snake oil salesmen and just opted for the lowest capital investment I could. A plug in resistive heater and a direct 300l cylinder. Total upfront cost about €800 and a suck it and see approach for the rest. Direct electric heating is expensive, even for a passive house (about €5/m2/yr) especially when you fall outside TOU tariffs which you will do without banking heat in a concrete slab or storage heater. Retrofitting anything is a pain too, I wish I'd been more proactive with ducting for example for an ASHP or putting a few more fuses spurs for a storage heater would have been very cheap.

@FelixtheHousecat I completely get the desire to buy a package, heating, cooling and DHW from a single manufacturer. Mostly with the ideal that it'll all play ball and work well together. However you're putting all your eggs in one basket. A recent post here has a member looking at chucking an entire €15k GSHP system because a ground loop has burst. In my opinion you're better off to stick to standard components that can be easily swapped out and competitively sourced in future.