Spinny

The other day it was hot in the house and my thermostats were saying 27C. They need calibrating and seem to overdo the actual temperature by a couple of degrees - so I would say it was 25C. However the outside temperature was only 21C. So despite the insulation in the new extension it doesn't seem to keep the house cool in summer. Why is the house getting hotter than outside ? Is it just the effect of sunlight coming through the glass in the bifolds, window, and 3 rooflights - warming the inside and the insulation keeping this warmth in ? Is it the slate grey pvc membrane absorbing heat from the sun, and despite having 150mm PIR underneath transferring heat into the extension ? Any thoughts ? (I remember asking my architect about aircon at the design stage and he poo-pooed it as not necessary or worth it in the UK. Seems a shame there isn't a way to run wet underfloor heating in a way that would cool the floors ?)

Any advice on this and on boarding reveals generally ? Is this reveal board with 6mm plasterboard and 14mm XPS worth using ? I am also wondering about how to put fixings into the reveal - for example I will want to put roller blinds in the reveal but they will be positioned alongside the insulated cavity, so how am I going to be able to screw them up ? Do I need to fix some wood or metal in place behind the reveal board that I can fix into ? Is it better to use a tile backer insulated board and is that then easy to fix into ?

That has always been my worry, but I cannot for the life of me find any way to find a good tradesperson. Internet reviews are meaningless and often fixed and fictitious. Recommendations are dodgy because often the customer just doesn't know the difference between good and bad - or else they are doing a favour recommending their cousins boyfriend. I have tried highly rated on checkatrade and they say they will come but never do. I have had 7 plumbers, 3 have done incompetent things, 2 never quoted, and 1 buggered off for 3 months immediately after starting work, and 1 blocked my mobile because I called him twice in 3 weeks enquiring after my quote.

A painter with a wall sander ? How does that work ? Is he sanding imperfections in the plaster ? How do you find a painter and decorator that diligent ?

I have already drilled a 20mm hole in position for an outside tap. I need to drill it out to 35mm to take the Frosti tap I have bought. I cannot seem to find a 35mm Masonry drill bit that does not have an SDS fitting (it needs to be over 300mm long). I don't own an SDS drill. Can I buy a converter somewhere so I can fit an SDS ended drill bit to my standard hammer/non-hammer (non-SDS drill). I see hundreds of adapters to fit a standard non-SDS ended drill bit into an SDS drill, but am yet to find one the other way around. (PS I only need to drill one hole. I have already drilled through the two concrete block leafs at 20mm with no problem using my non-SDS drill at 20mm. So answers that say 'buy an SDS drill' are not helpful to me.)

I think you need to talk to the architect. This an unauthorised deviation. Consideration needs to be given to the possible options to remedy the situation. Replacing it would be one, but there may be other options, the obvious one being to up specify the external waterproofing so that water cannot get into the cavity. (presumably the flood waters don't reach the DPC height) I only have experience of one extension build so am biased by that, but I'd say you cannot trust builders or tradespeople, you have to start by assuming that everything has to be checked until they show that to be unnecessary by their own conscientious actions. Builders don't necessarily even read the architects spec. The problem with building is that once a mistake is missed when it occurs it becomes very costly to put right later.

If you are plastering then a possible dividing point is the 'mist coat'. i.e. have the builder plaster and apply a mist coat to the plaster. A builder will assume anything not specified is basic and cheapest available. So specify e.g. skirting, architrave, coving, internal doors, hinges, handles etc. - MDF, timber, pine, oak ? Builders may just produce a quote with 'Estimate Only' for some sections or items. For example plumbing, or electrical work. You may need to insist they provide a broken down quote from their plumber or electrician against your defined specification. We had builders give an estimate only figure which was half the actual cost when it was quoted - good trick to make a quote look cheaper - but not what a customer wants. Our architect put provisional sums into the SoW where the spec was undefined. Also Provisional items are things to be quoted but you may decide to drop from the contract (e.g. to save cost). Don't forget once you sign with a builder and he is part way into the job, it will be too late to argue with him if you want an extra and he quotes you an exorbitant price for that extra. (PS We were only doing an extension not new build.)

We chose our own window, door, and rooflight suppliers. (I honestly expected much more input from the architect which was disappointing because you have to do all your own research and legwork and visits to see them in the flesh). We included them with their quoted prices in the building tender. However a builder will add 10% (plus VAT if applicable) on the price straight off, and will also charge for delivery, fitting etc. At the very last moment our builder suddenly took them out of his price. I have been told this occurs quite commonly because ordering custom size/spec doors and windows most often requires a very large deposit or even full payment with order - and delivery/install can be many months later. This then represents a large negative cash flow for the builder. He left the rooflights in, but we had to take them out too when he was completely failing to prepare an order in time for them to be on site at the right time. I had to work out the sizing including heights w.r.t. the roof slope/furring myself, and order the rooflights and matching upstands directly myself. We had the doors, bifolds and windows fitted by the suppliers. Seems the best way to me albeit you need the openings prepared before they can come to site to measure. Then they produce drawings for your agreement, then make to the drawings, then come and fit them. Means you are not dependent on a possibly dodgy builder not fitting them very well, it isn't your fault if they don't fit, you get a guarantee from the supplier/fitter, and if the builder has screwed up the opening they will call it out when they come to site - arguably you can charge the builder for a failed fitting. Our builder screwed up the bifold opening. There can be a LOT more to ordering the doors, bifolds, windows, and rooflights than you might think or expect. Lots of options these days - RAL colour, Matt/Satin/Gloss, handle colour, handle style, type of lock, opening direction, opening side, hinge colour, height vs FFL, trickle vents, style of frame, sightline on bifolds, type of glazing unit, cill ?, cill type, cill size, internal blinds ?, blind colour, corded ? And then you have to think about where you want the plaster line to be on the frame and how that might match with other adjacent windows. Is your builder (who won't live with the end result) going to carefully consider all that stuff ? A lot may depend on your budget, but often fenestration is a big part of design/look these days.

Nice little tip someone gave me for running hidden wiring for a video doorbell - run the cable up the post by taking the stop bead off and hiding the cable within the stop bead.

You could use a large cricket between the roof outlets to push flow outwards towards them. (You can google flat roof cricket) We have 3 rooflights and one is a long one against the wall so the wall below continues seamlessly up into it. The architect omitted to design any detail behind the roof light so we do get some ponding behind it when it is very wet. I realised their mistake only after the firing strips had been done and too late to organise any insulation crickets made from PIR to go under the membrane. Tis another of the gotchas you only learn from experience. Like putting your lighting plan up against the structural engineers beam and joist plan before you find you cannot put lights where you wanted them.

Looking at 240V motors, really don't fancy rechargeable and have put in the cables now. One blind company has said each blind should have it's own fused spur ? This seems a bit OTT to me especially for 3 blinds above a bifold needing 3 fused spurs. Each one only seems to draw 100W or so. Told blind motors need to be powered up individually for set-up, but surely that could be achieved by just disconnecting the other motors ? (Or adding an inline switch in the blind box.) Can anyone comment ? @Mattg4321 @garrymartin @Andehh @CalvinHobbes @nod Anyone

I am aware of aerogel as had it specified by the architect in the form of aerogel wallboard. Ironically for the same type of issue in the vary same room. Alongside the steels over the wall opening I also have a 1m piece of wall. This is a continuation of the outside wall of the house where the warm roof on the side extension abuts this wall. So again above the roof the wall is external, but below the roof it is internal. The architect said this wall must therefore be insulated and as I wanted the thinnest possible option came up with aerogel wallboard which has been installed. I have come across this one https://steelconstruction.info/images/5/53/SCI_P380.pdf which includes section 1.7 on condensation. This type of detail - steels to create an opening in an outer wall, must be so so common. So I am a bit dismayed there isn't a clear practical solution in common use. At this rate I am going to have to pay the architect exorbitant amounts to give me an answer. What the hell does everyone do ? (I am sure they are not commonly buying aerogel to install in every knock through extension).

OK. So If I have a 10M beam, and 9.5m of that beam are within a heated building at 21C and 0.5m of that beam is outside at 0C, what is the temperature of the steel beam ? Won't the internal innermost end of the beam be at 21C and immune to condensation. Meanwhile the outside end of the steel is at some temperature below 21C and above 0C and is radiating heat into the outside air. Bad for heat loss, but... How much of the internal steel must be insulated to protect it from condensation ? 10mm, 100mm, 1000mm 10000mm ? (The more length of the beam you insulate internally the colder the beam will get.)

OK. However in this case it is impossible to get continuity of insulation. Because the steels are bolted together and support outer leaf and inner leaf they will always be a thermal bridge (save removing them and inserting insulation above them - which isnt happening). Insulating the steels moves the bridging point but cannot eliminate it. Taking the case of say a steel which penetrates the insulation layer - what do you do ? You cannot separate the steel internally from the rest of the structure across its entire perimeter and length. You can insulate the steel close to the penetration, but at what point can you stop ? What is the temperature gradient in a steel beam ? If I put a bag of frozen peas on top of a steel in a warm room how much of the steel gets significantly colder than the room ? (I agree the thermal bridge is wicking heat out of the building. However given that can't be completely stopped, the other question is how can condensation be avoided ? If the room is 21C what temperature surface will it condense onto, and will the steel reach that temperature ?)

Thanks @JohnMo I really don't want to put 25mm PIR under the steels because (a) it will further reduce the already lowered ceiling height and (b) ceiling has already been battened into the steel level with the bottom of the steel ready to board up. I could put some insulating plasterboard under the steel and across the whole ceiling but it will have downlight holes and has to be fireboard under the steels. I guess the question is should the steels be treated as in the warm zone or the cold zone ? They are really in the internal warm zone of the ceiling void but just happen to have something of a cold bridge acting on one face. Whatever I do the steels are a cold bridge because they are bolted together. I either put them mostly in the warm zone, or insulate all around them putting them mostly in the cold zone. In this video the steel is on the inner leaf but has a cold bridge plate to the outside, but the answer is just to insulate the steel close to the cold bridge... https://youtu.be/1-qJc2BaXo0?feature=shared Is there some way to estimate the temperature the steel would reach ? (PS Does warm moist air percolate through rockwool and would it still condense on the steel - unless adding a vapour barrier too?)