HighlandHopeful

Hi John, thanks for your response. The SBSG is Scottish and for design of houses in Scotland. This might be what I have to do if below doesn't work. This is what we've started with in our building warrant application. I'm worried that the third party verifier won't accept SBSG-approach, so we'll be back at the beginning needing to get a structural certificate... on principle I want to stick to my guns and say if SBSG is suggested by BS then this approach should be verified, but worried I'm going to spend months in a stale mate and then have to get a structural cert anyway. Wondered if anyone had experience on this sort of scenario. Thanks, I appreciate your insight.

Hi all, We have designed our new home using the Small Building Structural Guide, as per Section 1.0.5 of the Building Standards Domestic Technical Handbook which states: "The Small Buildings Structural Guidance (SBSG) provides structural guidance to designers of small domestic buildings on how to comply with Standard 1.1 [of Building Standards]... The SBSG has been written for those with expertise in building design and construction but not necessarily in structural engineering design. Where the conditions or parameters fall outside the scope of the guidance, then specialist advice should be sought from approved certifiers of design, chartered engineers or other appropriately qualified persons." The proposed house being within all the parameters set out in the SBSG - including size, dimensions, height, pitch, loading, altitude, wind speed, snow zone, ground conditions, wall type and foundation type. Therefore in our building warrant application, we set out the design calculations as per SBSG. So we used this method, endorsed by the Building Standards, and sent off with the warrant application to be verified by the Council. The building warrant officer in their first round of comments have said that they don't have resource in house to verify our structural design themselves, so would need to use a third party, which could take up to 12 weeks, and did we want to instead go down the SER route to save time. I hadn't made my mind up on this, but thought I would contact some engineers on the SER to see what are options are. The two I contacted so far have said that the level of detail we have provided is not what they are used to working with, have declined to work with us and suggest we get an architect/engineer. But we have followed the methodology as set out in the SBSG endorsed by BS, including design for walls, roof, lintels, foundations, floor, and how to present the design. I'm a bit stuck, BS is saying it's ok to use SBSG, but then there are no verifiers available at the council, and if they go third party or we do, the engineers aren't happy to use SBSG... If this was never going to work out for us, I wish the BS didn't mention the SBSG, as I wouldn't have spent every weekend for months doing the structural design, calculations and drawings, if in the end I'm going to have to pay someone else to do it anyway. I'm not asking for advice about where SBSG was appropriate to use, I know it is as our house falls within all its parameters, and its use is referenced in the BS, just asking if you think I should stick to my guns and wait it out with the council, find a different verifier who is familiar with SBSG (I only contacted 2 on the SER, there are many more), cut my losses and pay a structural engineer to produce what we need to satisfy building control... Anyone got any encouragement, experience or pearls of wisdom? Thanks.

Thanks that's helpful when you say 'before you have the specifications for the cables' - who is it that will be giving me the spec for the cables. I think that's what I'm asking really. Is it up to SSE or is there a standard that I can buy? Thanks again.

Hello all, Just doing some forward planning - I am wanting to lay water pipe and electricity cable when our road is dug out, so that when Scottish Water and SSE arrive to make the connections they can do so and the pipe/cables are already buried as that will work better with our timings, not having to dig up the road again to lay pipes and cables. What I can't for the life of me figure out, is what type of electricity cable I need to buy to lay under the road towards the house. Sorry it's such a boring question, hoping there is a simple answer of what to buy Thanks! Emily

😃 thank you! ok off I go to get some Psi values (sigh)

hi, thanks for your reply. I read the guidance document manual as I went along and was v dilligent, the only thing I didn't change was kappa for thermal mass and the thermal bridging. I'm going to work out how to do those for my design and see if it helps. Did you do your own SAP assessment using a software, did you modify the thermal mass/thermal bridging inputs? Thanks.

Hello all, I have a trial for Elmhurst's SAP10 (1 week into the 2 weeks) and had a great time at the weekend inputting all my area info, U-values, construction type and openings sizes and picked our intended MVHR and ASHP from the inbuilt database. The only defaults I left in were a) I left in the default for thermal bridging which includes a Y-value of 0.200 b) I let it tell me the kappa values for the thermal mass of the walls/floors/roof which then calculates the thermal mass value. But then, I pressed the magic button to calculate everything and...... got a SAP score of 55D and energy/CO2 70% WORSE than the target property. Obviously terrible. Does anyone have experience with Elmhurst's SAP10? Is it that I shouldn't have left the defaults in? But why are they defaults if they are so inappropriate? The house is one story, 1-bed, pitch roof, 81sqm, u-values roof 0.11, wall 0.13, floor 0.15, UFH (yes you won me over!), ASHP (heating and DHW), MVHR - I'm not saying it is perfect, but how is the SAP so so so low and how is it so much worse than the target property? We only have one heat source, in case that makes a difference. I have the SAP of my niece's 4-bed house she is currently building which has higher U-values than us and only double glazed, and the energy and heat demand of our 1-bed is almost twice that of the 4-bed so something is obviously very wrong. What's weird is that I've tweaked loads of things to see what it is that is making it so bad, e.g. changing the floor area, reducing the openings, speccing a different heat source, and it only changes the SAP like 2-3 points in either direction. So is it the thermal bridging and the kappa values (i.e. the things I left as default) that make such a difference and I shouldn't have left in the defaults? Just wondering if anyone has experience with Elmhurst's SAP10 or other resources/software that does SAP that can shed any light. I have been trying to get in touch with Elmhurst but not hearing back yet so thought I'd see if any of you had any thoughts in the meantime. Thanks!

Hiya We have never really seen them with running water in... They are at the side of a dirt track down to the beach that was put in in the 80s to allow tractor access to lower fields at the beach. The ditches were part of that digging, so to allow surface run off from the track to go into the ditch rather than run down the hill and make the track muddy.

We have a couple of dry-ish ditches, so piping from the sewage treatment plant to the ditches (via a rumble drain if required) is our preferred option. I have read your responses to various threads on here - thank you, you are all so infinitely helpful! What I'm a bit confused about is what to start off with in the building warrant application, I want to go in confident with a solution (pipe to the ditch) but that's not listed as one of the solution in the Building Standards handbook, but do the BS people not care as long as you've done your option pros and cons relevant to your site and situation? The BS handbook says (section 3.9.2) that with very slow percolation test, options are soakaway mound, or any of the options for 'slow' that don't require infiltration, which are 'constructed wetland', a vague 'proprietary filtration system' (but is filtration infiltration?) or a vague 'other equivalent filtration system'. SEPA say talk to Building Standards department on this website here https://www.sepa.org.uk/regulations/water/septic-tanks-and-private-sewage-treatment-systems/private-sewage-treatment-system-registration-guidance/discharging-to-land-via-a-soakaway/ I haven't found anything more useful from SEPA (actual guidance docs) so if anyone has a reference that would be great. I saw your (ProDave) comments elsewhere about re-doing the percolation test to show the situation at ground level (i.e. 300mm cube at the top, rather than digging down to the 900mm of where we would have a soakaway if we had a soakaway), haven't done that yet but if I want to lead the BS people and SEPA to allowing us to discharge to the ditch, what is the benefit of doing the ground level perc test? Or is it because their next preference after a 'normal' soakaway is a mound soakaway so you have to go through that (and discounting it) before resorting to ditch discharge? For context for you and @saveasteading, our 900mm percolation holes drained 0mm and 40mm in 24 hours. They were done last week, obviously in winter, water table high and all that. The land where we are building the house is peat over clay, currently covered partially in heather. When it rains the rain wanders off down the steep hill in front of our plot towards a track down to the beach. The track has a ditch next to it (dry). The land to the ditch is in our/family ownership. Another option could be pumping up to a field (also in family ownership) and putting in a drainage field, but with those percolation rates, I think the drainage field would be bigger than the physical field. Thanks

Hi JohnMo - which SEPA guidelines are you referring to in this message, if you can remember? We had extremely slooooooooow drainage of the holes, it would be good to know what sizing guidenlines you are referring to? Thanks!

Thanks everyone for all your help today. I will go away and think about the floor.

Yes I am perplexed about why floor U value is so high, I wonder if I've calculated it wrong. I've used this for advice: https://www.gov.scot/binaries/content/documents/govscot/publications/advice-and-guidance/2020/02/tables-of-u-values-and-thermal-conductivity/documents/6-c---u-values-of-ground-floors-and-basements/6-c---u-values-of-ground-floors-and-basements/govscot%3Adocument/6.C%2B-%2BU-values%2Bof%2Bground%2Bfloors%2Band%2Bbasements%2B%2B.pdf The build up the floor is: On top of the soil, 50mm of sand, 50mm of concrete. Then 150mm air gap - as part of the calcs I had to imagine this sucking heat out through the floor and transmitting to the uninsulated parts of the foundations around the perimeter of the building. Then 150mm joists with 100mm rockwool in between (and a 50mm airgap) Then vapour barrier Then 2 layers OSB at 11mm each Then the wooden flooring but I haven't included the thickness of resistance of this yet, so U value might go down slightly, but not significantly. I used Resistance of the floor, Rf = 1/Uf - 0.17 - 0.17 And U-value of the floor, Uf = 1 / [(1/U0 ) – 0.2 + Rf] U0 was derived from the table on page 6.c.3 at the above link - our area to perimeter ration is 0.5 and the "Ventilation opening area per unit perimeter of underfloor space (m²/m)" is 0.003ish assuming that I calculate this by doing depth of air gap between soil and joists divided by perimeter.

Interesting, love the sound of the aluminium skirtings with UFH (although BFs dad very allergic to aluminium and will be helping with the build - does any other metal work?). Another reason against UFH for us, which I should have said, was that I thought you need a concrete slab for UFH, but we can't get a concrete tanker to our plot. We are having strip foundations so that we don't need a tanker.

Thank you for all of that, really helpful, I've updated my calcs to assume a much lower temperature, I'm not sure why but had it stuck in my head that you design for average lowest, not actual likely lowest. Re: how we are doing ventilation. I assumed 0.6 air changes per hour for the heat loss calcs as I read that passivhaus should aim for that. We are using heat exchange MVHR. Haven't got as far on that yet, but let me know if you think 0.6 is a stupid number to have put into my calcs! Thanks again, I'm chuffed you replied.

Thank you for helping! I've calculated our U value of walls 0.131, roof 0.105, floor 0.21. We have a lot of windows, which are 1.1 ish. For heat loss I used: Qp = ((F1 x Sigma AU)+(0.33F2 x NV)) x (tc - tao). F1 and F2 were taken from the textbook for panel radiator systems and were 1.00 and 1.10 respectively. Sigma AU was the sum of all the areas of elements multiplied by their U values N was the air change rate - I assumed 0.6 V volume of the house tc 21 degrees and tao WAS -5 but I've edited to -15 as I get now that I need to design for worst case as we won't have supplemental heating, not for an average case. I thought about it for a long time but I really want wooden floors and lots of rugs and carpet in a couple of rooms... Thanks for the other info, incredibly helpful!!!