Iceverge

Neglecting to nominate a third party to oversee quality control is a very common error we make as self builders. Assuming building control will do it is also a mistake. They only ensure the building isn't obviously dangerous and otherwise " close enough" to the regs. You can pay a project manager or architect or engineer to oversee but it's expensive so most folk just leave the builder to get on with it. The results are variable unfortunately. In this case, you as the client are unexpected having to step into the role. It's not pleasant but most of us have been there and made the same errors so are willing to help. Please post more wide angle photos of how far the work has progressed so far and we will try to suggest the best remedial action so you can get a good result. Please post sectional drawings etc too with your name removal so we can try identify some potholes further down the track.

The trouble is that unless the boards in the cavity are sealed to the inner leaf and sealed to eachother you'll get wind blowing behind them and they may as well be sitting out in the garden at that rate. The same wind will blow through the blocks, ( Blocks are like rice Krispies cakes, very porus). This wind will make it's way out sockets, around skirting and your extension will be very cold. Again your extra insulation is doing little unless you prevent the wind from blowing through it. Either start from scratch or use a closed cell foam like Walltite or Technitherm to completely fill the residual cavity . You could pull out the boards that are there and use EPS beads instead. Your U value will be about 0.3 but still perform vastly better than the existing situation.

Cellulose is dearer than Rockwool but that includes fitting. About €150/m3 plus VAT near me. Not sure of UK prices. There's a notable difference between the cheap mineral wool "loft roll" and higher density batts like Rockwool so ensure you're comparing like for like. Cellulose has the advantage that it really helps the airtighess too when it's properly installed..

I'd have thought the opposite, certainly financially. No massive deposit to be paid up front with stick build and you could avoid a crane too if you were able to lift a few timbers

Kingspan will direct you towards their own products and have a habit of playing fast and loose with some of the specs. Tragically this has included some of the fire tests too. Ubakus is free when you make an account and you can choose genetic materials. https://www.ubakus.de/en/r-value-calculator//? What are your aims for the wall. What kind of U value do you need? Are you stuck for internal space. Pics/sketches would help.

Building control wont care. It's been done on every street in the country for too long. The easiest method of rectification is probably to inject or pour some closed cell foam outside the insulation to seal it to the inner leaf and take care of all the gaps. You could bollock the builders and get them to repeat the work they've done but there's no guarantee they'll do it better the next time. It's a flawed design in my book but a very common one.

Is the construction a warm roof is the question I think. The following are all warm attics but not all warm roofs Is your insulation : A. All above the rafters? ( Warm roof) B. Above and between the rafters? (Hybrid roof) C. Just between the rafters? D. Between and below the rafters?

I think these are pretty much covered with dMEV too which was what I was recommending as a starting point and I estimate comparable long term costs to MVHR with less up front initially. Hole in the wall insulation is really just hope for the best and I don't think anyone should consider it for a house in 2025. I'm certainly an advocate of MVHR though.

In that case I would have expected them to build the inner leaf first and then set the insulation boards clipping them tight to the inner leaf. How exactly are they fitting them at the moment? In my view they should be foamed to the inner blockwork, to eachother, around the wall ties, the foam trimmed and then all joints and exposed edges taped with foil tape. I've never seen it done though.

Internet thinks woodcrete would be fine underground........ I was thinking of EPS however, it will perform every bit as well as an insulated raft as a foundation provided you get your thresholds right.

Any pics of the board install? It's very tricky to do well. In fact I don't think it's actually possible in real life. Batts and EPS beads are almost fool proof by comparison. What is the remaining cavity depth after the boards?

There's more to consider with MVHR too. 1. Noise from outside. 2. Filtered incoming air 3. Heat load ( how big a boiler you need) 4. The stability of the internal temperature. 5. Drafts. 6. Insects in the house. Hard to put a more accurate price on these. However as I posted elsewhere recently Airtightness and MVHR are far more important than extra insulation so perhaps they might be a better place to trim if you're really stuck for cash.

In the real world mechanical ventilation is a must if you value the quality of the air you're ingesting. I would never suggest anything else as a sensible option. MEV works well, but to have some control over the infiltration, you'll need humidity sensitivity wall vents (about £60 each). Say you have one per bedroom and living room maybe 7 in total=£420 Then add dMEV in every room with a tap. Maybe £70 x 5 = £350. A little bit of additional wiring and fitting and you'd have a well performing ventilation system for £1000. For a 200m² house it'll cost roughly 3000kWh of extra energy to be used annually. Say £250 extra annually on heating. Electric will be much the same. There'll be minimal servicing but allow maybe £70 per year for a dMEV needing replacing. £320 per year for a 200m² house isn't too bad. 20 year cost £7400 A bit of shopping around will see you buy a new MVHR unit and the bits for say £4k. Allow £2k for install for some reasonably handed builders. It'll cost you £40 per year in filters and the bearings will need to be done every 4. Allow £100 per year in maintenance. 25 year cost £8000. There's very little in it long term in £££. Break even is about 20-25 years I'd estimate.

Plain string with nothing tied to it is often fine to get pulled through a duct by a vacuum. Your situation sounds unfortunate but not to worry, we're all learning and in the grand scheme of things, it won't be a major life regret. The plan to dig, add an accessible junction box and run a bigger duct is probably the best options at this stage. This stuff isn't that dear.

It'll be fine. I hope you're using full fill EPS beads or mineral wool batts.

Congratulations on your new house. Perhaps more details of the current state of it might help us guage what kind of heating system is most likely to be most comfortable and efficient in the long run. Some houses are terminally unsuitable for an ASHP but this depends on, 1. Airtighess 2. Insulation levels 3. Window spec 4. Footprint 5. Occupancy patterns. Perhaps you could give us an idea of some of these. At the moment it sounds like a gas boiler might be best if that's what you currently have installed?

What about strip foundations and ICF rising walls?

I'd be putting that in the "pro" box for conventional footings. Nobody will care as much about details as you. Can you trench fill for the footings in dry weather? With good digger operator and it's one of the simplest footings you can make. Superb performance can be achieved with any kind of foundation so long as you look after the thermal bridging which isn't rocket science.

Our builder used timber bolted to the steel, cement board screwed to the timber and rendered over with sand and cement to match the render on the blockwork. Wish I'd insisted on using concrete lintels now. I'm not keen on having timber buried in the outer leaf of the house and there'll inevitably be some voids in there which means that moisture may be able to corroded the steel. Ideally I would like steel: 1. Completely encased in concrete for rust protection or 2. Under/behind some insulation to keep it warm and ensure no moisture condensates on it to start with..... What I would do in your case. 1. Tac weld or drill and fix some heavily expanded metal mesh to the web of the steel. 2. Fill the web of the steel with concrete entirely. May require some partial shuttering and then poking with a trowel but it's not rocket science. 3. Apply more expanded metal mesh over the whole lot. Use some self drilling screws underneath to secure to the bottom. Better still tac weld the mesh directly to the steel, (you'll need a MIG welder for half an HR). Let the mesh overlap well onto the blocks too to prevent cracking and fix it with a few screws. 4. This will leave a flush and well keyed surface to directly take a coat of sand and cement render. Following this process you will have 1. Steel complete encased in concrete. 2. Thermally uniform substrate for the render to avoid differential heating and cracking.

Our actual measured heat usage was a bit more, 3.2MWh/annum. Not sure of why the difference to PHPP. The insulated envelope of our house is essentially a 8.5mx13.5mx5.5m box so a good form factor like you say. We're quite a distance further south than you too. What was your blower door result and window spec?

Delight is pushing it!! Given the labour and uncertainty involved in renovations it's a pragmatic decision.

Probably not. Maybe if you were to have a lighter superstructures like timber frame. Have you considered a basement?

As an aside 3G, Airtightness and MVHR were always going to be included for the comfort, noise, air quality and building health aspects. Payback was considered but it wasn't really ever up for discussion given the other benefits.

OK here are some numbers for our 185m2 house after having a play with PHPP. Out annual heat demand is 2625kWh. Passiv windows with 3G , 200mm EPS in the floor (u = 0.16) , 250mm EPS bonded beads in the walls (0.15) , 400mm Cellulose in the attic. (0.1) Airtightness 0.31 ACH50. Here are some Airtightness figures. 0.31 ACH = 2625kWh 1 ACH = 3012kWh 2 ACH= 3586kWh 3 ACH= 4170kWh 4 ACH= 4716kWh 5 ACH= 5537 kWh 6 ACH= 5861kWh Now I play the same game but step back the other fabric of the house individually to say a bregs basic house of a few years back. Floor U 0.3 = 3103kWh Wall U 0.235 = 4005kWh Roof U 0.175 = 3159kWh Double Glazing = 3387kWh Lose MVHR = 5365 kWh Keep the airtightness and MVHR but use the poorer figures everywhere else 5918kWh MVHR and airtightness are the biggest wins. Then come glazing and U value. This isn't as straightforward to generalise as window areas vary, a bungalow will have much more wall than a 3 story town house. Insulation has to be improved all together really. Not much point in adding 50mm to the attic insulation when its already at 500mm. It only reduced the U value by 0.008W/m2K. However if you add 50mm to 100mm wall insulation it takes it from 0.4 to 0.26. 16 times more of a difference. I concluded in our house for the above insulation types the ratio of increasing the insulation in the following ratio was the most economical. YMMV depending on construction specifics. 4 Floor 5 Walls 8 Roof Hope this helps.

For any UFH you need lots of insulation in the floor or otherwise too much of the heat will be lost downwards. The more the better but start at 150mm PIR or 200mmEPS. This means digging up the existing ground floor and lots of labour. For an old leaky house you need high power heat emitters for quick response. Radiators are the easy way to do this. If you go for UFH you need to have it in a thin screed and closed spaced pipes.