epsilonGreedy

6 lpg bottles = about 4000 kWh annually which is excellent even for a mid sized 120 sqm house. Many here build much larger. I wonder if you would get an A EPC rating now with your improved PV, ASHP, MVHR setup?

If you are still on bottled LPG I guess your actual annual heating cost is acceptable regardless of the EPC rating.

Your feedback on heating demand and the insulation thicknesses you provided earlier indicate a high spec build thermally speaking. If powered by mains gas you would get a B EPC rating I assume. I pay £64 per 47kg LPG bottle = £0.098 per kWh (92 litres x 7.08 kWh per litre). EPC is a cost per sqm rating. The cost per sqm difference between B and F is 100% or a doubling in heating cost. Bulk LPG is about 30% cheaper than bottled. I know new builds on bulk LPG with slightly better insulation than building regs can get a C EPC rating. Based on actual heating costs you should get a C or D EPC on bottles and a B EPC bulk lpg. The EPC rating formula must use a daft kWh unit price for bottled LPG.

So-so wall u-value, a mis calc in the floor u-value and the thermally challenged shape of a bungalow.

I would ask for a refund or very detailed explanation of that assessment score, sounds odd to me. How does the property perform thermally speaking?

And the floor. To sum up a bungalow has a greater proportion of external surface area to floor space compared to a 2 or 3 storey cube shaped house.

It is best applied from a bottle similar in size to a bottle of fairy liquid no larger than one litre with a nozzle.

After fitting about 300 slates I have been surprised at how robust they are. I broke my first slate this week when I copper nail would not bed down flush, I had left my ear defenders on after trimming a slate with an angle grinder and could not hear the hammer collisions.

☹️ Sounds like another reason to fit roll top lead flashing ridges and hips. Much simpler to peel back the flashing and relay a section of slate roof. Having said that a mortar bedded ridge on conventional tiles will start to loose chunks of mortar bedding after 15 years because the underlying wooden roof structure moves. Traditional roofers claim fancy dry ridge systems eventually suffer UV breakdown in the bits of exposed plastic. Nothing is problem free for +25 years.

Yes but just my contrarian view. Those who sell branded anhydrate liquid screed sound convincing when promoting a thin screed but is this because they sell mainly to pro builders who look to shave a few ££s here and there. When I get to the point of planning which insulation sheet thicknesses to buy to make up a finished floor 225mm high I will try and phone some technical departments to establish if there is a downside to going a bit deeper than standard. I also need to get my line laser out to create a topographical map of my current block floor heights. I know of one 10mm dip mid floor but hope the periphery is within +/- 5mm.

Would you prefer a bit more thermal inertia in your slab? Is your floor base level mm perfect? If not might an extra 10mm of screed cover up some errors? The thinnest flow screens are very runny. A set floor that leaves some UFH pipework exposed constitutes a major disaster. History is littered with the failures of over confident engineers. My inclination when I arrive at this decision point will be to design for 60mm if a manufacturer claims 50mm will be ok though will need to ensure the extra depth does not generate too much heat and trigger an excessively fast cure.

Ok. I was thinking that thermal expansion/contraction cycles might open up hairline cracks in slate but now I understand that freezing water can drive that as well. When you say the slate "bursts off" do you mean a large flake of slate breaking away in the plane of the slate rather than a fracture through the thickness of a slate? This is very true. I feel people over simplify the quality issue down to Country-A = Good and Country-B = iffy. I think it depends on the quarry and the seam of slate being mined at a point in time.

On a similar theme we should keep the last remaining coal generation capacity available for years but I fear the climate change lobby will demand its destruction. At present we routinely spin up 2GW of coal generation capacity when the wind is having a slow day. Over the next 6 months two more nuclear stations will close for good due to engineering defects at those plants, think that amounts to 1.5GW of lost capacity.

It is a geopolitical dilemma but I do not see the moral dimension. The drive towards Zero Carbon will eventually eliminate this dependency, until then why would we worry about which pipe Russia chooses to deliver gas to us. I worry more about the Mafia running Her Majesty's Government and their £100 billion money printing collusion with the Bank of England. Borrowing against the future of unborn babies will end in tears.

Anyone care to guess where the unit price will go if the military standoff in the Ukraine turns hot? https://www.theguardian.com/news/audio/2021/dec/16/is-vladimir-putin-preparing-to-invade-ukraine-podcast As I type 52% of the UK's electricity is generated with gas, 6% from wind and 13% from European interconnects. What worries me most is that a nice little war is just the political tonic for a beleaguered President Biden.

Given your stage of planning the book titled The House Builders Bible will give you a good breakdown of total costs. In the latest edition the author includes alternative building methods since many self builders adopt new building techniques.

In this thread your expertise is now hidden behind a paywall.

That is good. Always makes ense to cross check that the open market will value the final result at no less than your total project spend. This is just a sanity check even when building a forever house. At a very rough guess I think the split is 50% to water tight shell and across the whole project materials/labour is another 50/50 split. You need flesh out this concept and create your China shopping list. List the items here and see what people think. 85% of Britons live in a property with under 180 sqm of internal floor space. 450 sqm is a ginormous multi millionaires mansion.

No need, I did the calcs. The u-value difference between 200mm and 300mm of XPS insulation is 0.04 W/m2K. Assuming £0.09 per kwh of heat input, then dropping to 200mm of insulation adds £30 to the annual heating bill or possibly less because in the shoulder months the UFH slab emits less kWs into the house and hence the slab temp is lower.

@Zak SYou need to go back to the beginning and ask some fundamental questions. When you purchased your plot with a large 180 sqm bungalow, what proportion of the plot value was for the building? Is it habitable? For example if the property cost £350k then it is likely the market value was assessed as £200k for the plot plus £150k for the building in need of £50k of upgrades. Why do you want to spend serious money demolishing this large structure to replace it with something only 25% bugger? Why do you need to build something well over 200 sqm? A couple can live very comfortably in a house with 130 to 160 sqm of internal floor apace. What grounds to you have for thinking that you can beat the market on sqm build costs by sourcing from China? If it was such a good idea the industry would be doing this already. I doubt more than 25% of the material inputs to a house structure could be sourced at a sensible price from 10,000 miles away by sea. The existing property is presumably structurally stable which contrasts with your view that knockdown and replacement with a raft foundation is the route forward. Without building trade skills and 1000's of hours of hands-on labour you will be unlikely to better £1500 sqm build costs during a period of runaway material price inflation and labour shortages. Do you have the cash to fund the £300k build plus another lump sum to demolish and cart away the debris? In your position I would visit another architect with proven skills in property renovation or extension and see what could be evolved from the existing structure. Replacing the roof could gain you 8 tons which would then allow some lightweight small upper floor to be introduced to provide 45 sqm of upstairs floor area. Insulated plasterboard would boost the wall u-value. Wood cladding or other exterior finish could rejuvenate the street appeal of the existing structure.

Nope the temp of the slab is principally determined by the heat loss of the main house in the case of the OP. The extra slab temp required to cope with the extra loss of heat through 200mm of insulation compared to 300mm is very small. I recall that when using Jeremry's heat loss spreadsheet for 150mm of insulation, ground heat loss was 8% of total space heating without UFH and 12% with UFH.

A bit on the high side, 29 degress would be a reasonable temp to model with. Ok but now express that in extra heating ££'s per year for 200 sqm of internal floor space for both 300mm and 200mm of insulation.

He is talking about the high-end of Passiv House trendy foundations. Still a bit niche but growing in popularity. Your average local builder will look confused if you suggest this type of super insulated raft foundation. 150mm of rigid PIR floor insulation is pretty good but a bit more pays off if fitting underfloor heating. 200mm is way better than most new builds, 300mm is phenomenal but only makes sense if you apply the passiv house ethos to the rest of the house structure. What is you budget for this build? I think it is relevant before you decide to knock down the existing large bungalow. Has an expert told you the existing foundations won't satisfy a building inspector.

My guess is that providing there is a continuous bead of mortar filling 50mm of a block joint width then the mortar joint is airtight. Pointing can be deceptive because it could result in a thin crust of mortar being smeared over a joint with a void.

@Faz How does a hard frost trigger failures in a natural slate roof? Let me guess: Temperature extremes open hairline fractures in the slate? Or Water under one slate in the overlap expands and levers a slate upwards at the nail fixings? I have been up on my roof this afternoon fitting natural slates and now I am worried.