Dreadnaught

I have a simple DIY OSB cubicle on site sitting on a couple of pallets, knocked-up by one of my groundworkers, with white goods and a flexi to the nearest IC. Bucket for flushing. But I also have access to proper facilities next to the site.

I have my SAP calculation for my forthcoming bungalow and all generally looks good. The roof and floor have U-values of 0.08 W/m².k. However, the walls are a bit low, about 0.18 W/m².k. I did this on-purpose to maximise floor-space but it has turned-out a bit lower than I expected so I am thinking of adding an additional layer of insulation inside the the airtightness layer of say 25mm or 50mm of PIR. I was planning a 25mm service void anyhow. My questions: Could I just fill that service void with sheet PIR everywhere except where services run? That would do the job without stealing more floor area. I am aware that electrical cables may need de-rating if they are insulated. To counter this, could I just leave, say, 50mm air-gap each side of a cable run? Are there any other problems with largely doing-away with a service void by filling it with insulation? (For service runs, as a bungalow with a warm roof I will have 200mm of open space between the metal-web joists in the flat roof). (The external walls will be 240mm I-beams at 600m centres full-filled with blown-cellulose/Warmcel.) (The airtightness layer is Pro-Passiv Smartply.) (I am aware of condensation-risk analysis and I am confident that adding such a small amount of extra insulation won't cause a problem).

Keep in mind that I am building this dwelling primarily for my enjoyment of the process and journey, and as a learning experience. I am therefore optimising for my own involvement, which is close to full-time, not for the usual triad of price, time and quality (although from that triad, I choose price and quality over time). I'm sightly reluctant to name names on this public forum as it may be unfair to those I did not choose. I would be happy to send you a PM with the names. In general terms, my long list was about eight frame-companies. I visited the factories of two and spoke at length with about four. Unusually, I was quite opinionated about the frame build-up that I wanted and so was looking for that flexibility. In the end I chose the company that offered that flexibility and which also happened to be a local company, not halfway across the country. I learnt, with the benefit of hindsight, that it is perfectly possible to take a different approach. Having now also been introduced to an excellent and personable frame designer, next time I might start with them and ask them to recommend a frame-manufacturer in the local area of my next build, wherever in the country that may be (frame manufacturers are the clients of frame designers). I learnt that it is perfectly possible to work with the various parts of the supply chain oneself, such as pile designer, foundation designer, frame designer, roof designer and make it all work, and not resort to using a one-stop shop, with the inevitable constraints that provides. I didn't choose a standard package but invented my own. Its a bungalow: Foundations: a complicated and completely bespoke solution. Screw piles, 240mm heave protection, 230mm PIR insulation (not the more usual EPS), reinforced concrete raft (with UFH pipes and lots of other pipes and ducts embedded within it, including the potable-water distribution pipes). Three embedded recesses in the concrete (two shower-formers and a mat-well for the front door). Frame: 240mm I-beams full-filled with woodfibre insulation (either Wamrcel or woodfibre batts, I am still choosing). No internal walls: I will do those myself in metal framing. A single steel beam. Flat green roof: warm roof, by Bauder for the transferrable warranty and no worries about leaks. Bauder is also installing the extensive green-roof atop. Six windows. Nine roof windows. Passive-house-style front door (the only external door). I chose this as I had read a lot about frames and wanted my chosen balance between thickness (which steals floor space), U-value, decrement delay, acoustic insulation, and greenery (saving the planet). I will be interested to see how this frame preforms. Yes, two of the big national firms did. But that was actually of no interest to me as I want to do the airtightness process myself anyhow to see what sort of results I could achieve. – (By the way, I simply could not have done this without BuildHub!) Hope that's helpful. Of course, it is only one personal view and, as you may have gathered, I am somewhat unusual in my motivations for building. Others, and there are many here who have much greater experience than I, may be able to provide insights that align more closely to your own personal circumstances.

When is an Intumescent Pipe Collar needed?

How would I seal the outer face? Foam around and then just tape the duct to the breather membrane?

Could someone explain how to make an airtight seal for the supply and extract ducts to atmosphere please? The ductwork work will be 160mm Aerfoam insulated mass flow ductwork. My external wall will be a timber I-beam wall at 600mm centres. Cladding will be brick slips. Is it simply a matter of cutting the holes through, inserting the pipes and then using a pair of airtightness grommets on the inside airtightness layer?

On the subject of silencers, I notice the Ubbink Air Excellence 800-series manifold box has the option of putting sound attenuation foam within the manifold itself. It is shown in this video. And it seems you can buy extra attenuation foam pieces too to bump it up yet further, although I am not sure about this. Could such a manifold also act as a silencer too I wonder? Two birds with one stone.

Ask away. My frame is in the very final stages of specification and is due to go in to production very soon and will be erected on site hopefully the other side of Easter. Having chosen my frame company more than a year ago, I remain very pleased with my choice. They are a friendly relatively local company and it has thus far been a joy to work with them. They also introduced me to a splendid frame designer and it has also been a pleasure to work with him, albeit lockdown slowed him down as it has for many people with families.

I read your reply with care. Really interesting and highly relevant. Thank you very much. Regarding doubling ducts, what about pressure as well as noise from turbulence from within the pipes. For all longer runs, wouldn't doubling ducts also reduce pressure, which in turn would reduce how hard the fans need to work, which I turn could would reduce noise from the appliance itself. Any merit in such reasoning too? And given that ducting is not a big cost in the overall costs, suggest doubling long runs as a matter of course? Oh yes, I forgot about that document. Thanks for the reminder.

Thanks @Iceverge. When you say 90mm is that the external dimension? And internal would be 75mm? Is that right? 2.5 m/s noted, thanks. I am thinking of using Ubbink Air Excellent System, which 90/75 duct and even higher capacity one that is semi-rectangular in various sizes. Ubbink has good data on their website for each component showing volumes, flow rates and pressures, which are very hopeful. I have calculated my room sizes on-the-back-of-an-envelope, which has been helpful in deciding on duct numbers and sizes. For example, I have quite a large living room and was thinking of putting two supply outlets, each with two 90mm ducts attached. Four ducts in total. Running the numbers showed that a single 90mm duct to each of the two outlets would be fine but, conversely, one single outlet with two ducts attached would have been border-line noisy.

Do I actually need someone like BPC to design my MVHR ducting system? For my new-build bungalow, it seems really simple. I have designed the ducting plan myself following the basic rules: equal number of supply and extracts across the house (5x of each) double pipes to every terminal so it is quiet supply to bedrooms and living room (x3 & x2) extract from bathrooms, kitchen, utility room and plant room (x2, x1, x1, x1) room terminals as far from the door as possible Seems simple! What am I missing? Is a pro-design for the air-change data, which is needed for building control? The reason I am thinking about this now is that I am just about to put the timber-frame in to production. The frame has one single structural steel. And that steel would benefit from some pre-cut holes (x6) to allow the 75mm MVHR ducting to pass through it. I can cut the holes based on my design. Or should I get a professional involved?

Welcome @Phaedrus! There's a few us around East Anglia self-building. I'm in Cambridge and @Nick Laslett is in Suffolk as two examples.

Resurrecting this old thread. The MVHR extract vents in my kitchen either need to go though a steel beam or can be a linear diffuser in a wall without needing cut a hole in the beam. But I am still not sure whether linear diffusers are good as extract terminals. I wonder, has anybody used a linear diffuser in their MCHR system? @MikeSharp01, did you use one in the end?

I'm doing this now. We will be boxing out the foul risers under the showers for the concrete pour. The pour will hopefully be next week or the week after once it warms up. I'm having wet-room shower formers too in my passive slab, which made things extra complicated. Probably wouldn't do that next time.

Yes, I'm going for the extra fat, super-insulated version in this design. 1.5m wide so a bit wider than in the image. Black escutcheon (yes I didn't know either: keyhole) unlike in the image. That's a bespoke groove pattern by the way.

Unfortunately not. The entrance door is close to 1.5m wide however, which could help. Do have a 2.5m x 0.8m roof window over the kitchen. Sofa delivery by helicopter could work if all else failed.

? Thanks guys. Now I have to work out how to convince RK Doors to lock-in the price for a year. Anyone tried that?

I am resurrecting this old thread as I am watching the cold weather now for my concrete pour for my insulated raft foundation. Anyone else doing the same? At the time of writing (February 2021) it looks like overnight temperatures will not consistently rise above 4ºC for another month (!?!) in Cambridge if long term weather forecasts are any guide. And then my concrete team will probably have a backlog of pours to do. Patience is a virtue – I need to be more virtuous!

I am just about to order my front door, an expensive RK-model. I am worried about this pricey door getting bashed and scratched during the build. Unusually, I only have a single external door into my whole dwelling – no back door. Would it be better to pay a chippy to put in a temporary entrance door now and delay the installation of the expensive one for a year, until the end of second-fix? Did everyone else do this? I have seen entrance doors covered with protective sheeting. Does that really work? How is it attached? (My current progress: just about to pour my concrete raft foundation – when the weather warms-up. Am currently ordering the doors & windows, etc., so they all arrive soon after the timber frame goes-up.)

Thanks @Timedout & @Russell griffiths! Helpful insight! I've think I have found a local air-con merchant that stocks it. I will pop over on Monday and see if they will sell me some. My concrete contractors are on site so I don't really want to wait for mail order if I can avoid it.

Does 10mm pipe-insulation exist? Neither toolstation nor any of my local plumbers merchants have it. They all only seem to stock 15mm. Is it that 15mm pipe insulation fits snuggly on a 10mm Hep2O pipe? (I will be using it to lag my Hep2O pipes as they emerge from my insulated raft-foundation.)

Thanks @Russell griffiths. As @DevilDamo says, in my experience the arboriculturalists have a way around every objection that a council tree-officer can raise. Ingenious fellows! But you are likely to get a long list of planning conditions related to trees to sign-off as you build.

On @dpmiller's ingenious idea of using a Urinal-PIR sensor to empty the dead-leg of water, how about a cobbled-together Smart-home solution like this: - a 15mm Solenoid Valve Nylon (normally closed), 230v version, like this, £21 - A smartplug (Homekit, Alexa or Google Assistant, etc.) - A PIR sensor (Homekit, Alexa or Google Assistant, etc.) ← I would have this anyway for the lights. The PIR sensor triggers the smart plug, which opens the valve for a set period. Could even program it not to trigger again for a set period. Why might that not work? I suspect there are some reasons. The solenoid:

Ah, I actually calculated it for 10m not 15m. Sorry. In reality the length is about 13m or so. Note that 15mm is the outside diameter. I think the internal diameter of 15mm Hep2O is 11.3mm (wall thickness being 1.85mm). (11.3/2)^2*3.15*13 ≈ 1.3 litres

I wonder if that would be audible.