Iceverge

Interesting. Please keep us updated with pics. Have you considered moving the DPM above one layer of EPS to prevent it getting punctured? How do you plan to run the UFH?

Good stuff. What was the build-up of internal wall insulation in mm and order of layers? It's a less covered method here. Any floor renovation?

Well done on getting planning and welcome. Pics and plans always welcome! I think @Kelvin is a fellow heb homes builder and there may be a few more about too.

Concrete is normally cheaper than screed but needs care to get a good finish. You could omit the screed altogether and just put two layers of OSB glued and screwed together floating on top of the insulation. This could give you up to another 50mm to play with and certainly wouldn't crack.

Your scheme is to try to emulate the effect of trapping a layer of gas between two planes like a double or triple glazed window. This only works if there is no convection. In your case you want to actively promote convection above the insulation to ensure the roof can dry out. In reality anyway you will find it impossible to create a layer of air between two materials without any convection and a layer of simple mineral wool would aid the insulative effect more than your DIY cavity. I don't quite understand this. There is a case for a low emissivity (shiny) barrier for heat protection in very sunny climates with no ventilation below the roof covering but it makes almost zero difference in a heat retention setting.

A few more pics if the room as is would help. I think to get any satisfactory result you"ll need to move the radiator and raise the sill of the window at a minimum.

Ah yes. Can you get to 150mm as a minimal. The. 175mm, 185mm and 210mm on the other areas to make it level. I expect you'll have joints anyway at the doorways so this should take care of any differential movement. If you are worried about cracking in the middle of the room you could use 70mm concrete with 10mm chip and plasticiser with some steel mesh powerfloated to finish.

You have a total of 25mm for insulation or 25mm difference?

No issues. Just use the Maxim amount of insulation you can. How much depth do you have to make up?

I would say it'd be prudent to block the top of the cavity to prevent any EPS beads escaping if you full fill it later. From a fire point of view it would preferable too. I would stay away from PIR between the rafters and use a 50mm mineral wool or woodfiber batt and then more insulation below the rafters. Something like Rockwool Flexi or steico flex. Woodfiber is particularly good for summer overheating protection. Ease of fitment, noise, heat protection, fire, cost, thermal drift, are areas that PIR doesn't cover itself in glory.

Easy with rads and TMV I assume?

Yes you're right. If you add grid losses at about 7-8% into it where do we end up?

Wrap the whole building in plastic in situ. Guttering, slates, birds nests the lot . Nothing too technical, maybe like that black stuff they put on pallets, or bales of grass silage. It should be reasonably durable once out of the sunlight. Erect a 4 post portal frame outside it with a metal pitched roof. Then wrap the frame in some of that cement impregnated fabric they use for military huts and canal reinforcement. Wait for a rainshower to allow it to set .Then pump the void in between with EPS beads. Exhaust source heat pump for DHW and ventilation and A2A for heating. Windows and doors optional.

Tying it to m² has little benefit I would argue, just more unnecessary complication. The vehicular analogy would be an "A" rated lorry @ 10MPG or 0.0025Gallon/Mile/Tonne Vs a "B" rated hatchback at 50MPG or 0.013Gallon/Mile/Tonne. Twenty times worse on the face of it. The EPC rating for houses gives the impression that if we all drive efficient 18-wheelers our problems will go away. In fact it promotes the building of larger houses as on a per m² basis as they're easier to achieve a low kWh/m2/annum than smaller houses. This will increase overall energy use. Adding solar production to balance high winter losses caused by poor building fabric exacerbates emissions until we have some viable interseasonal energy store. Take house 1, a glass masterpiece with poor form factor and average glazing etc. Uses 10000kWh per annum for space heating but thanks to a generous solar array generates 8000kWh in the summer. House 2 has no PV but is super insulated. 2000kWh/ year space heating. They have the same EPC rating but there is an 8000kWh difference in bought in winter electricity say at 50% fossil fuels means the solar PV house would use 4000kWh more of FF energy. Bonkers. Houses should be rated at kWh/annum in my opinion. Keep renewables out of it and offer proper feed in tariffs for that part of the game. Similarly specific heat demands out if the picture. It's counter productive.

It's bonkers complicated. How about kWh/year. Much like MPG for a car. At the moment an enormous house with average heat loss but with a deathstar worth of PV on the roof can be A rated. It'll still cost a fortune to heat in the winter.

The UK has historically been a strong economy globally, GDP per capita was high and the cost of energy was relatively modest on an individual's pocket. When I lived there I was always surprised at how terrible house windows and doors were. Drafty sash single glazed items with solid timber frames from the early 20th century were the norm. They all disappeared in Ireland in the 1990's replaced by not so pretty but vastly thermally superior PVC double glazing. I suspect it was because we had no money then and couldn't afford to heat our houses otherwise.

@RichardL like you I think A2A is a sensible option, even for for old properties. @Hanksy did a few posts a year or two back demonstrating this. Unlike ASHP you avoid heating any fabric (UFH) which in uninsulated houses is a black hole for energy use. A good unit can be installed for maybe £1500. One in the hallway or living room of every gas boilered house could significantly reduce gas demand (provided the power stations run on something low emission) . Minimal disruption Vs ASHP and better COP. Leave the gas in place for topping up cold rooms and DHW.

70mm screed 100mm insulation 25mm sand blinding 125mm concrete slab (with A252 mesh) How about. ( With your SE's approval) 100mm concrete slab with mesh Slip membrane 300mm eps/200mm PIR DPM This is what the builder did on ours.

Yes, I'll replace it with something like OSB soon I think. My logic was that there will be so much airflow through it that all small particles and off gassing will get done pretty quickly and become inert .

I think the idea that if you design it well and insulate it sufficiently then you can run it at very low flow temps. That means that if the floor is at 25⁰ and the room is already at 25⁰ due to sunlight/woodburner whatever then the water passes through the UFH in that area without actually emitting any energy. It'll give proportionately more energy to colder rooms than warmer ones. Hence no zones. This won't work with high temp rads at 70⁰ for example as they'll still emit heat as the room will always be colder.

We had an airtightness of 0.32ACH which was bout 4900mm2 of open area over 600m2 of envelope. A glance at some ventilation charts suggests 550mm2 per kW of installed appliance so even in our house we would be able to have a 8.9kW appliance. A CO detector is still a good idea in case of a blocked flue etc but I wouldn't worry in the slightest about the ventilation in your case.

Bought Amtico from ebay and stuck it down myself. It needs to be super flat so SLC is a must I think. It's only been 2 years but I suspect it'll last until the next ice age. We also have some click fit LVT from Pergo, oak effect, fitted floating not glued. Much simpler to fit but nowhere as tough as the Amtico. Also floating wouldn't be my choice again as it has bubbled slightly in 2 of the rooms. It is far warmer underfoot than normal tiles and substantially more forgiving for children falling and dropped plates etc.

‘The field tests show that a siloxane impregnation, if properly applied, can repel rain water to such an extent that a complete drying of the masonry is possible… It seems possible that inappropriate impregnation can even increase the moisture content and hence the danger of frost damage… The quality of workmanship and the preparation of the façade, for example by repointing it, appear to be of major importance. If the quality conditions are met, an impregnation can be considered as an effective rain protection. ‘The field tests show that a siloxane impregnation, if properly applied, can repel rain water to such an extent that a complete drying of the masonry is possible… It seems possible that inappropriate impregnation can even increase the moisture content and hence the danger of frost damage… The quality of workmanship and the preparation of the façade, for example by repointing it, appear to be of major importance. If the quality conditions are met, an impregnation can be considered as an effective rain protection. Small cracks up to 1mm do not affect the rain protection if they are thoroughly impregnated and if the walls if of sufficiently low air permeability, e.g. by the application of a plaster on the inside.’ Künzel & Kieszl (1996) This suggests if done well it is a valuable addition.

Sounds like the most fire safe house on the planet. Is that a brush on or spray? Did you rate it?

Welcome welcome. Any chance of a plan sketch of what you'd like. Maybe some photos too of the similar styles that take your fancy.