Rishard Posted February 13, 2022 Share Posted February 13, 2022 Having built several extensions and barn conversions, it’s time for my own self build! I’ve been using this site for the last year getting upto speed with similar approaches and practices. I’m through planning and lining up our next few moves. I opted for an ‘almost passive house’ style build with plenty of insulation and reduced thermal bridging details having consulted the green building store during our design process. Having worked and built several projects I’ve seen the varying scale of acceptable build quality in real site practice. Being my own project I’m hoping to achieve near passive standards without the certification process. Our site has a few limitations due to neighbouring houses shading and the classic north facing garden. We are also in a conservation area. All this being said, we have planning. My first question to the forum would be on PHPP. We did plan to model the house but can’t get this done till summer with GBS. I have other architects who could help but at a large cost. I know some people have been happy to progress based on tried and tested detailing ect. Is it worth the spend for piece of mind? Is it too late in the game to make vast changes to our approved planning anyway? Would love to hear peoples views on this phase. One issue I have would be to accurately size our space heating needs without understanding the predicted building performance. Slap me if I’m over thinking so I don’t overspend! Cheers Link to comment Share on other sites More sharing options...
ProDave Posted February 13, 2022 Share Posted February 13, 2022 Hi and welcome There is a heat loss spreadsheet made by @Jeremy Harris on here that many including me have used to model our heating needs and it proved very accurate. This is something you can do yourself. As to actual performance, that is largely down to detailing, it is possible to fit insulation so badly it might as well not be there if you don't care or don't know what you are doing. Where are you building and what construction method? 1 Link to comment Share on other sites More sharing options...
tonyshouse Posted February 13, 2022 Share Posted February 13, 2022 I generally advise a building physics model of the house, this has generally informed additional shading, reducing the size of dangerous west facing glazing. will tell you exact heating demand and how much overheating you will get, I used TAS and paid but a good friend ran the excellent Hot 2000 a Canadian open source programme now hot 3000 I think, will help and both my models informed no formal heating needed, max heat demand for whole house 100W in October, maximum on coldest night etc all very useful Link to comment Share on other sites More sharing options...
Rishard Posted February 13, 2022 Author Share Posted February 13, 2022 Great, I’ve read about people using this spreadsheet. Is it fairly manageable for a builder? Construction will be. Block, full full cavity, block. There will be a brick plinth detail and a combination of render and cladding. On plan we have 300mm dritherm cavities following the Denny dale approach. Metal web joists, glue lam ridge beams with potentially warm roof vaulted ceilings. Plywood window reveal boxes and triple glazed windows. Dense block for walls with a course of thermal block work at concrete slab and above a steel to carry part of the 1st floor. 1 Link to comment Share on other sites More sharing options...
Rishard Posted February 13, 2022 Author Share Posted February 13, 2022 4 minutes ago, tonyshouse said: I generally advise a building physics model of the house, this has generally informed additional shading, reducing the size of dangerous west facing glazing. will tell you exact heating demand and how much overheating you will get, I used TAS and paid but a good friend ran the excellent Hot 2000 a Canadian open source programme now hot 3000 I think, will help and both my models informed no formal heating needed, max heat demand for whole house 100W in October, maximum on coldest night etc all very useful I’ve not heard of these programmes. I had hoped to outsource this part of the work to someone more capable than myself to avoid error. It was very much my plan, only slightly scuppered by their availability which made me look into alternatives. I’ll look in to TAS. Link to comment Share on other sites More sharing options...
Gus Potter Posted February 13, 2022 Share Posted February 13, 2022 (edited) What's you gut common sense telling you? If you have lots of west facing glazing then overheating is a significant risk. If you are trying to shave a bit of the capacity of the heating system to deliver / make savings.. then.. if you have kids the doors get opened and left opened! Teenagers tend to open a window to have a fag or throw up out of them after socialising, you may too! Lastly remember that from time to time we may get 15 -20 deg Celcius.. would be a shame if this happened at Xmas when you have all the family round and you can't warm the house up for those who are frail say. Seriously though North light glazing is a cracking concept particularly if you are say a painter..or the like. Edited February 13, 2022 by Gus Potter 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted February 14, 2022 Share Posted February 14, 2022 9 hours ago, tonyshouse said: a good friend ran the excellent Hot 2000 a Canadian open source programme How is Paul, good bloke. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 14, 2022 Share Posted February 14, 2022 9 hours ago, Gus Potter said: Seriously though North light glazing is a cracking concept particularly if you are say a painter..or the like. The rear of my house is NE facing, where I tend to live. The art college at Camborne (where the School of Mines was) has huge north facing windows, was great to lecture in, and had a fantastic view. Link to comment Share on other sites More sharing options...
Rishard Posted February 14, 2022 Author Share Posted February 14, 2022 (edited) @Gus Potter- my gut feeling is to try have it modelled. The main reason being this is my first low energy build. Although I’m confident with the detailing and build-ability of the project I have little understanding what this may look like in terms of its efficiency. Knowing some of the figures would help inform how best is can heat the building. Likewise, I’m not trying to scrimp on having a sensible heating system that can deliver heat when it’s needed. I have small children who will one day be those teenagers you talk of! I have a readily available supply of wood offcuts from my work so did think of a small log burner. I know this may be seen counterintuitive but just a thought. I’ll await other peoples views on this…. We have no west facing glazing due to neighbouring boundaries to west and east. Glazing to both north(garden) and south. Edited February 14, 2022 by Rishard Link to comment Share on other sites More sharing options...
Rishard Posted February 14, 2022 Author Share Posted February 14, 2022 On 13/02/2022 at 21:34, ProDave said: Hi and welcome There is a heat loss spreadsheet made by @Jeremy Harris on here that many including me have used to model our heating needs and it proved very accurate. This is something you can do yourself. As to actual performance, that is largely down to detailing, it is possible to fit insulation so badly it might as well not be there if you don't care or don't know what you are doing. Where are you building and what construction method? Do you know if there are any instructions for filling this out and interpreting them? cheers Link to comment Share on other sites More sharing options...
ProDave Posted February 14, 2022 Share Posted February 14, 2022 46 minutes ago, Rishard said: Do you know if there are any instructions for filling this out and interpreting them? cheers Here is the original thread about it Link to comment Share on other sites More sharing options...
Iceverge Posted February 14, 2022 Share Posted February 14, 2022 I paid €800 to a guy who in hindsight did a half assed PHPP for me. After that I downloaded the manual and started playing with it. Most of it doesn't need filling out unless you are getting certification. It would easily save it's price (about £150 i think ) in optimising insulation. We ended up at 200mm EPS floor, 250mm EPS beads in the cavity walls and 400mm cellulose in the attic based on an hour spent checking where our € made the most difference with phpp. Jeremy's spreadsheet gives very similar results but doesn't calculate overheating which can be significant. If you just want to know you max heating load and you are planning on building thermal bridge free + airtight+ MVHR then a simple calculation will do. Just measure the outside of the house like PHPP not the internal. The internal heat gains from electrics etc cancel the MVHR losses and other sundries. (External Floor area * U value) + (total external wall area * U value) + (external roof area * u value) + ( Window area * U value) Add them all together and multiply by your maximum temp difference you'd expect on a cold day. (114m2 *0.16) + (232m2 * 0.13) + ( 114m2 * 0.09) + ( 30m2 * 1) = About 89 * ( 20 deg difference in the south of Ireland) = 1780 W total heating load. PHPP gives 1497W. Either way a 2000W heater will do ( and is doing) the trick! By the way we didn't bother with a stove due to dust and smoke inside as well as the trouble getting them beyond passive levels of airtightness. 2 Link to comment Share on other sites More sharing options...
Rishard Posted February 15, 2022 Author Share Posted February 15, 2022 @Iceverge- Cheers for that calculation. I’ll certainly give that a try. Seems a bit more my level of workings out. Like you, I have a designer offering the phpp service for around the £900 mark. What cavity ties did you end up using. I know these contribute towards a thermal bridge so would be curious to know how bridge free I need to be. The cost difference is fairly high by comparison and I’m wondering what other people have used. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 15, 2022 Share Posted February 15, 2022 4 minutes ago, Rishard said: What cavity ties did you end up using. I know these contribute towards a thermal bridge so would be curious to know how bridge free I need to be Keep things in perspective. You can easily work out the exposed surface area of a wall tie, and how many there will be. That, along with the length and the thermal conductivity o the material they are made from can easily be translated into a U-Value. Then look at what percentage that will be of total losses rom all other elements. In a similar fashion, you can work out the cost difference and compare it to the total spend on insulation. Link to comment Share on other sites More sharing options...
joe90 Posted February 15, 2022 Share Posted February 15, 2022 Conversely someone here or another forum worked out the cold bridge due to wall ties on a house was so small it was not worth the extra cost . Diminishing returns and all that. Saying that I did no calculations whatsoever for my build, I went with gut instinct (after other buildhubbers did their calculations) and I copied!. 1 Link to comment Share on other sites More sharing options...
Rishard Posted February 15, 2022 Author Share Posted February 15, 2022 @joe90- I like the sound of that approach. After working building all day, coming home to then calculate everything starts to hurt my head. Hense why I was look to pay to have phpp done for me so I can focus on what I do best. Did you follow any of the above calculations for your heating system and mvhr system? These 2 things are the subjects I know least about. Link to comment Share on other sites More sharing options...
joe90 Posted February 15, 2022 Share Posted February 15, 2022 3 minutes ago, Rishard said: Did you follow any of the above calculations for your heating system and mvhr system? No, pure guesswork ? I guessed my heating load from another previous buildhubber who had a similar sized house (and I got a cheap deal on Ebay so took a punt, the MVHR unit I bought, again on EBay was oversized but cheap (bankrupt stock), do you know what, I have never got round to balancing it even. note, I recently had a heating problem but that was my fault with a design presumption with the buffer tank (I can’t get it all right ?♂️). Link to comment Share on other sites More sharing options...
Iceverge Posted February 15, 2022 Share Posted February 15, 2022 4 hours ago, Rishard said: What cavity ties did you end up using. I know these contribute towards a thermal bridge so would be curious to know how bridge free I need to be. The cost difference is fairly high by comparison and I’m wondering what other people have used. Stainless Ties from Vartry Engineering in Wicklow. PHPP is excellent for such calculations. Opting for basalt ties would have taken our annual heating demand from 2599kWh to 2575 kWh. It would have saved €3.12 per annum. Given the astronomical cost of basalt ties the payback was over 500 years! That said you'll never regret putting in too much insulation. If doing it all again I would do 300mm EPS in the floor, 300mm in the walls and 400mm in the roof at least. 1 Link to comment Share on other sites More sharing options...
Rishard Posted February 16, 2022 Author Share Posted February 16, 2022 500 year payback! That’s that decided then. It’s sounding more and more likely to run phpp. If not just for piece of mind. I was planning mineral wool in the cavities. Is eps better for resisting moisture? Did you use a raft or trench foundations? Link to comment Share on other sites More sharing options...
Iceverge Posted February 16, 2022 Share Posted February 16, 2022 Trench foundations. The EPS beads worked fine. You need to make sure the cavity is kept clean however. Ideally using a board to catch the morter drops. We used the beads right down below the floor level eliminating the need for the rigid boards as per the denby dale detail. Mineral wool would be better in a fire, but if the fire gets into the cavity you've had it anyway. Good thread here. Link to comment Share on other sites More sharing options...
gravelrash Posted February 16, 2022 Share Posted February 16, 2022 Basalt wall ties cost me 25p each...a damn site cheaper than stainless...still have a load of 365mm ones left over...brain fade after all the design and planning! Link to comment Share on other sites More sharing options...
Rishard Posted February 16, 2022 Author Share Posted February 16, 2022 @gravelrash-Where did you buy your basalt ties? Ta Link to comment Share on other sites More sharing options...
gravelrash Posted February 16, 2022 Share Posted February 16, 2022 ahh.. theres the crux. 1 minute ago, Rishard said: @gravelrash-Where did you buy your basalt ties? Ta The basalt wall ties are the same as rebar, supplied mainly from Russia or china...Companies buy it in 500m rolls and chop it up to length, stick an o ring in the middle, oh and new design has some bungs on the ends so you dont poke your eyes out but are generally removed on installation. I bought the 7mm rebar from orlimex.co.uk which came in manageable lengths of 2.5m at £1.20 a length-possibly gone up now. bought a bag of o rings of Ebay, chopped up the basalt to length and rolled the washer on. No they are not BBA certified but Structural engineer checked and signed them off as suitable. Link to comment Share on other sites More sharing options...
Rishard Posted February 16, 2022 Author Share Posted February 16, 2022 @gravelrash-Still a worth while endeavour by the sounds of it. I’ll not rule it out yet! Link to comment Share on other sites More sharing options...
gravelrash Posted February 17, 2022 Share Posted February 17, 2022 On 16/02/2022 at 19:28, Rishard said: @gravelrash-Still a worth while endeavour by the sounds of it. I’ll not rule it out yet! When you consider that teplo charge £3.75 + vat and I needed 700 it was well worth a few hours of boredom 1 Link to comment Share on other sites More sharing options...
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