A_L

If you want to heat intermittently then it is probably better to have the insulation above the slab. If you want to heat 24/7 and perhaps try to use an off peak type tariff then insulation below the slab gives a greater storage capacity. There are other methods to fix UFH pipes e.g. rails https://underfloorparts.co.uk/product/underfloor-heating-clip-rail-track-1mtr-adhesive

More construction details required but if this is 290mm of Frametherm 32 then worst case is better than U=0.15 with the details you gave yesterday U=0.11 but it really should be one layer either above or below the slab depending on the response time/storage capability you want U about 0.19, making the 20mm layer 75mm would give about 0.12 That,s about U=0.11

If you go below 3.0 you will need a formal ventilation strategy. Page 19 here https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/468871/ADF_LOCKED.pdf

If the ground floor is a 19 x 7.5 metre rectangle, 150mm of PIR or anything else of equivalent thermal resistance will give a Passivhaus level 0.11 U-value. Personally I think you need another 100mm on the walls and 75mm on the sloping ceiling (same material) to get U values down to 0.12/0.14

This is relatively poor at probably not lower than U=0.25 If this DIY shed loftwool, thermal conductivity 0.044W/m2 .K then the U-value will be around 0.13 U--value around 0.20-0.22 With the floor area and external perimeter I can calculate a U-value

contact the Energy Saving Trust, https://energysavingtrust.org.uk/about-us/contact-us/ and ask about the Energy Company Obligation (ECO) and anything else locally.

@Russell griffiths, Something like this perhaps? https://www.klokow-gmbh.de/en/Fastening/Wood-joints/Tension-anchor/Simpson-Strong-Tie-Hold-Down-HTT.html

To be clear, it is the total area of external walls, ceiling, floors, windows. The actual U-values and relative proportions of these are irrelevant.

No, they are not. If using non-approved details a method using the area of external fabric elements is normally used. In a heavily insulated building it can easily add 30%-50% of the fabric heat loss to the total heat loss.

This is the leakage rate expressed as cubic metres per hour per square metre of external surface area. The area being measured on the internal surface of the external walls, floor and roof.

Electric ones use up to 1.5kWh per cycle at up to 2000W https://www.gaelforcemarine.co.uk/en/gb/Cinderella-Classic-Electric-Incinerating-Toilet-220-240v/m-4256.aspx Apparently there are also gas (propane) powered ones.

@SteamyTea , @jack , @pocster et al, Steamy is however correct, the insulation of a cylinder (pipe) is subject to the 'Critical Radius of Insulation' below which insulation actually increases heat loss. e.g. https://en.wikipedia.org/wiki/Thermal_insulation - 'look for insulation of cylinders' about 1/3rd down page

no, that makes it high emissivity. It is deemed to have a thermal resistance of 0.18m2K/W page 11 attached pdf BR_443_(2006_Edition).pdf

because of the ventilated cavity you should remove the thermal resistances for the associated softwood/air space/wood cladding, but you can insert an enhanced exterior surface resistance, add a layer of 0.09m2 .K/W to correct. does the VCL have a shiny surface? it needs one to get the enhanced thermal resistance for the unventilated cavity

@WWilts, Dritherm Cavity slabs are rated for 'full fill'. Silver/Graphite/Grey bonded EPS bead, conductivity 0.033/0.032W/mK with any block with a thermal resistance less/equal to 0.18W/m.K would get to your U-value. i.e. 100mm block/100mm bonded bead/100mm block. It could possibly be top filled.

0.15 increases annual heat loss over 0.12 by about 1.7kWh/m2/yr (full SAP, central England)

@Big Jimbo, here is one, https://www.changeplan.co.uk/u_value_calculator.php

@Buzz, strictly speaking it will make no difference to a pressure test as any open chimney should be sealed before the test, but 40m3/hr will be added to the SAP ventilation rate.

if that is a dT of 30°C relative to a dT of 60°C (80°C/50°C) output is about 42% It is one or the other, if they were in series the return from the radiators would be to high a temp for the heat pump to provide a useful COP. Goes for ASHP/Willis to. the DNO will want to limit the size of the heat pump to maintain the supply, typically a thermal output of 14kW is the maximum HP size for a single phase install.

under no circumstances buy this piece of greenwash from what I can find they are noncondensing so about 85% efficient when new, minus 1.0% per year for its age a litre of oil holds about 10.5kWh, using the efficiency compare with your favourite electricity tariff not a chance, at best you will get 5p/kWh for export only possible if you have a spinning disc meter, even if you do you are required to inform your supplier how? they will still have to pay their supplier for electricity through their meter, even if it actually came from you Sorry! ?

Moving the external door inwards will increase the exposed perimeter and reduce the floor area leading to a higher floor U-value. There will be an increase in the external wall area leading to a higher heat loss, the newly 'externalised' wall may also be thermally inferior to the original external wall. The changes would also increase the allowance for thermal bridging. All factors which lead to a poorer epc

Since the cavity (layer 5) is fully ventilated layers 5 & 6 are by convention not included but the external resistance, which is actually at the outside of layer 4, can be increased to 0.13 because the reduced average air movement increases the thickness of the external surface layer. See page 12 of attached pdf. BR_443_(2006_Edition).pdf

@Jason L , it is correct ?, it is roughly the basic elements of a Passivhaus build in our milder climate. N.B. it does not include about 2500kWh/yr for DHW!

Usually that there are plastic parts in the input to the boiler which cannot take water above 30°C from solar thermal heated water stored in a buffer before the boiler If you insulate opaque building elements to 0.11W/m2.K, windows to 0.8W/m2.K and infiltration to 0.6ach@50Pa and fit MVHR, average CH heating requirements can be around 800kWh/yr and at this level the low capital cost of a Willis type heater (immersion in a pipe) can offer a cost effective alternative system.

Changing to Dritherm 32 could make more carbon savings than adding 100mm to loft insulation if walls have greater m2 than roof and improve wall U-value to about 0.24