JohnMo

I have a wooden garage with steel roof. Mine is surprisingly cool inside, full sun most of the day. So metal roof, breather fabric, sarking board on roof rafter, 100mm accoustic mineral wool between ceiling joists, 25mm PIR below, fully taped. Walls similar, but without the 25mm PIR, just used silver bubble wrap.

But you need at least 6 of the solar collectors linked to give 70% saving in DHW in July. So realistically you could have 9 or 10, so are over £1k just for panels, which is in the 30 evacuated tube price range.

If your leakage rate is greater than 3m3/m2 @50Pa, keep your money in your pocket. As cost to run v savings made will not be a benefit to you. I would instead (irrespective of your leakage rate), look at a demand based MEV or dMEV, more cost effective to purchase, simpler to install, run and maintain and only ventilates at the rate required.

All my 50mm battens are fixed with 90mm nails, unless they are screwed to woodcrete. I have all the ceiling battens and the second layer of external battens (for vertical cladding) all nailed with 90mm

I looked at those and for a house need quite a few, which ended up being quite expensive.

This how I did mine. Nail into the side of the rafter, so the nails have to shear, rather than just fall out. The center section were skewed nails.

Your boiler has weather comp built-in. Go on to heat geek website and have a read up on weather comp.

Confused, what's not condensing? Condensing with natural gas starts with a return temp of 54 degC and lower. The lower the return temp the more condensing that occurs. The more efficient the boiler becomes. With UFH there is no point heating water up, to then mix it down to a cooler temp.

Ours was £4k with slate hearth, the flue, air supply pipe, full labour and Heta Scanline 8 full soapstone. Costs don't stop at just the fire.

If it's UFH, why are your flow rates to high? Seem high temps.

Don't buy a big sand hill. Views great, but landscaping costs are huge. Less glass, or Aircon from day one. More solar. More insulation. No more than one thermostat in the whole house. I had loads caused loads of issues with the heating and short cycling of the boiler.

12 degrees makes it a normal roof, less than that it's a flat roof. But the third person today that wants to miss a designing it correctly stage and make up as they go along.

Insulate

Why are you doing building work without proper structural engineering input. Flat bar will do nothing for you structurally. Primer does not provide rust resistance, it is porous to provide a key to finishing coats. It will rust in no time at all.

We have almost stopped using the recirc extract, just put the MVHR on boost job done. Only really use for smelly cooking.

Can't understand why you would build and not have a structural engineered design and then follow it. I like the Scottish rules, no structural design certificate, no warrant, no build. Keeps everybody right.

With all boiler types you get a big drop in efficiency, every time you go through a start cycle as all the metal parts soak away the heat during the heat stabilisation phase. Reduce zones as much as possible, no small zones, try to reduce central heating flow temperature so boiler has to run for longer. Low and slow, is the way to go.

I used Passive house systems Hi-Thermia Reflective Membrane. Has a mesh woven in doesn't tear, easy to work with

There was another thread a few weeks ago on the same subject, they concluded it was possible. Have a search.

We have a 3.1kW if panels installed and saw 3.05kW being generated, so no issue with mounting direct to sarking boards. I did quite a bit of research before mounting direct to sarking boards. Everything I read led me to the conclusion that in Scotland, it's not an issue with overheating, and if there is an issue your performance drops while the panels are too hot. Southern England may have an overheating issue, but they get better PV production.

Is putting the modules on the walls an option. You get better winter output, your electricity delivery curve becomes flatter, instead great in summer rubbish in winter.

There are issues with oversizing. The modulation range of the heat of pump, usually about 2.5:1 This is not an issue when at the lowest temperature outdoors, but becomes apparent when the outside air temp is in the 5 to 10 degC range. At 11 degC outside your heat demand is half your design case, so about 3kW. If your heat pump cannot modulate to that level, you then need a buffer added to the system.

Where's does the 12 or even 16k come from, the original post said 6 and 8kW. Sounds a big heat pump for an ICF new build. Unless the house is huge. My house, 190m2 single storey, lots of glazing and a 70m perimeter, but at -5 I have a heat demand just over 3kW. What does your SAP EPC, say your heat demand is?

To comply with MCS regs he has to do a proper heat loss calculation. This is a contractual document. He cannot put his interpretation on things, he should not use rules of thumb etc. I believe to comply with MCS installer rules he is to quote you before and work commences and get the bus grant If he's a lone contractor tell him what you want or he is off the job. If he's from a bigger company, get his boss to site and ask him to show you where in his installation regs it states you can apply rules of thumb and "what if" to heat loss calculations.

The other way to look at the heat loss. Say you have an airtightness of 2m3/m2 at 50Pa., Your infiltration rate is 0.1358. So inputting that in to a ventilation heat loss calculation Qv = 0.33 × n × V × ΔT watts. So say your volume is 300m3 0.33 x 0.1358 x 300 x 22 = 295W So at an airtightness of 2 if your house has a volume of 300m3 your ventilation heat loss without MVHR is 300W. If your house is is bigger small just change the 300 figure. Rules of thumb do not apply