MortarThePoint

That's a great price. I was paying £1.153 each in June last year down near Cambridge. As soon as I had a quote from one BM, the job was known and I got the same price form others.

Even with the top alternative insulation below, it may be difficult to get the space below airtight if not achieved by the ceiling.

I'm trying to understand resilient bar installation. For it to have any acoustic benefit, it is essential to avoid short circuits like a screw going through the plasterboard, resilient bar and into the joist above. It's all about isolating the mass of the ceiling from the joist. "Where Resilient Bar is being used for ceilings the bars are fixed at right angles to the underside of the joists as close to the perimeter of the room as possible without touching the walls" (link) In the video below they use a silicone type sealant at the board edges, but it doesn't look very convincing from an airtightness perspective. I will have areas above the ceiling near walls that are exterior vented. I have some questions that anyone who has considered this before will likely have worked out: Airtightness: How best to airtight the ceiling at its edges with the wall? This could be done at joist level, so maybe I need a membrane above the resilient bars. Wet plaster: Can we just wet plaster into the ceiling corner and is short circuiting the ceiling to the wall is less of an issue? Plaster cracking: Will the plaster crack at ceiling corners as it is possible the ceiling may shift relative to the walls slightly?

Probably, but if the formaldehyde concentration being higher near the floor is true, then it's a consideration for anyone who is interested in the formaldehyde part of this thread so I thought I'd share it.

Saw this and thought it may interest this discussion if someone comes here. I don't know mch about MVHR, but the height of room extraction may be a factor. https://www.novofibre.com/health/indoor-aqi.php

As an example, my copy of SPON's has 7.0N Hemelite @15.51/m2 and 3.5N Hemelite @ 15.76/m2, so 7.0N cheaper than 3.5N.

3.6N feels a bit on the low side to me for load bearing. Has the Structural Engineer specified 3.6N? There may not be much of a price difference between 7.3N and 3.6N. There was a point in time when I had 4 types of 100mm block on site (7.3N Stranlite, 7.3N Stranlite paint grade, 7.3N Fibolite, and 10.4N Stranlite). I wouldn't do it again that way. Structural Engineer hadn't called for anything more than 7.3N for 100mm blocks so wasn't critical.

D'oh! Too late for that unfortunately.

Mounting the plasterboard on Resilient Bar (or Resilient Channel as the US call it) could be a useful approach. It reduces my centres to 400mm or 450mm and also helps reduce sound transmission: I think this may be based on two layers of plasterboard, but one would still give benefit. https://onlineinsulation-sales.com/resilient-bar-rb1-45mm-x-16mm-x-30m-138-p.asp

Don't know what I was thinking, it should be called 'Site Club'

I could start a new 'Gym Club'. The rules of which would be: Don't talk about Gym Club Carry these 15mm plasterboards through this cunningly devised assault course

The nog-tastic approach has the option of reduce size boards (1800x900) but I expect they are probably expensive compared to the normal sized board

Would I want this for fire resistance as well? I think 3 storeys requires 30 minutes and on 600mm joist centres the table below says 15mm if using Wallboard. That said, the White Book where that table comes from has lots of different and somewhat confusing tables. I'm going to get bored of carrying heavy sheets of plasterboard through the scaffolding.

I wasn't clear in my original post. I was planning to use 12.5mm plasterboard, but wondered if the plasterer's concerns were based on experiences from when plasterboard was more often 9.5mm. Would stepping up to 15mm, from 12.5mm, negate the concern and give a good stiff ceiling? It's the first floor ceiling and we have attic trusses above with living space. The service gap could be handy for running pipes and electrical cables, but I can route those OK near the eaves on top of the trusses I think.

I need to attach plasterboard to the bottom chord of trusses that are on 600mm centres. The plasterboard will then be wet plaster skimmed. The plasterer has recommended adding counter battens (e.g. 22x100) at 400mm centres. That works out as a lot of metres of batten to install. Is his concern reasonable or more based on 9.5mm plasterboard than the usual 12.5mm? I could go up to 15mm if that helps.

Windows will hopefully last a long time, but glazing units don't do they? Does anyone have data on the life expectancy of glazing units. Naively, one could assume a triple glazed unit has half the mean time to failure of a double glazed unit if there were two independent points of failure. They won't be independent though, but I'd be interested to know how they compare. My calculation only considered the carbon cost of the glazing unit.

I see this as were triple glazing comes into its own. This approach is about eliminating weaknesses and that would invariably be the windows if not more than double glazed. In a house that is designed to be less thermally performant, something like an ASHP is needed in which case the windows can be evaluated on their own merit rather than trying to minimise there impact on a broader passive house type objective.

? I don't fancy living in a house with all the charm of nuclear bunker Lots of manufacturers appear to use the same frame and hardware for double and triple glazing meaning that 3g may actually be more 'flimsy' as the frame and hardware are working harder. Feels a bit like a Gillette advert and look where that's ended up. Are they on 5 blades now? In countries with <0C for prolonged periods of time it makes a lot of sense. If you double the dT in my calculations the COP of the ASHP suffers and so the 'carbon' payback time will come down a lot, perhaps to ~3 years. Also the apparent warmth will be more significant too.

You wouldn't be required to meet the prevailing building regs at that point, but are you thinking it would make the house more sellable if you did?

I have wondered about the perceived value in the market if the house was up for sale.

My wife mentioned that she read an article that said a triple glazed (18C) unit is about 2C warmer than a double glazed (16C) unit when a single glazed unit would be at 1C. It was based on a 21C room temperature, but didn't say what the outside temperature was. That means it's 3C colder than room temperature on the surface of the triple and 5C on the double. I can see that would affect convection and the feeling of warming if right up near the window.

We have our own bit of woodland and will likely mostly be burning fallen timber that would rot in a less environmentally friendly fashion otherwise.

I'm confused by the motives of going for triple glazing as I like to do the maths behind these sorts of things. I see two primary reasons economic, reduced energy bills, and environmental, reduced 'carbon footprint'. I am pro green tech so start from a bias of wanting to include them. Improved U-value: The U-value of a 1m2 window might typically improve from 1.2 W/m2K for double glazing to 0.8 W/m2K and so an improvement of 0.4 W/m2K. Based on heating the house for the coldest 6 months of the year (October to April inclusive): Difference in U-values, dU = 0.4 W/m2K average temperature difference across window, dT = 13 K (around my area for these 6 months, 19C inside, 6C outside) Duration, t = 183*24 = 4392 hours Window Area, A = 1 m2 Average heat flow, Q = A.dU.dT = 1*0.4*13 = 5.2W Annual thermal energy, E = Q.t = 4392*5.2 = 22.8kWh per year [Ignored: A double glazed window lets in more light (8% nominally) so there will be more solar gain in those months. That might work out as (guess) 50W/m2 and so an 4W difference between the two windows, but only for a fraction of the time so may amount to 1W average]. Ecomonic If heated by ASHP the 'efficiency' will vary, but I pick a value of 3.5 to be representative. With an electricity price of 14p/kWh that equates to a cost of thermal energy of 4p/kWh. That makes for a cost saving of 4p/kWh * 22.8kWh = 91p per year. Electricity prices could go up, but the cost uplift of triple glazing is >100 times that annual figure. The cost is all upfront as well. Environmental A triple glazed unit contains many extras, but most obviously includes an extra sheet of glass. Energy required to make glass, 21.9MJ/kg [1] Density of glass, 2.5kg/(m2.mm) (2.5g/cm3) Area of glass, 1m2 [overestimate as neglects frame width] Thickness of glass, 4mm Mass of glass 2.5*1*4 = 10kg Entrained energy in glass, 21.9MJ/kg * 10kg = 219MJ = 60.8kWh Energy debt payback time based on oil heating, (60.8kwh / 22.8kwh) = 2.7 years Energy debt payback time based on ASHP(SCOP=3.5) heating, (60.8kwh / (22.8kwh/3.5)) = 9 years There will be other uplifts in manufacturing 'carbon cost', but 9 years is a significant payback time and all that 'carbon' is upfront in manufacture and doesn't consider renewable sources of power generation that will come online over the next 9 years. Also, I would guess that glass manufacture is less likely to be using renewable sources of energy than the domestic electricity suppliers. I could believe that payback time heading beyond the lift of the unit. What am I missing here? Are the perceived benefits different? [1] https://www.sciencedirect.com/science/article/abs/pii/0166309781900614

I'll be using mine so infrequently I'm not concerned about the virbration H&S concern. If it was a concern about vibration causing issues to materials etc I would be more worried.

Harming the user's hand?