Clark Kent

This is really interesting, I’m doing a similar refurb but cannot dig out the ground floor. This guy isn’t either and adding no insulation at all and yet reckons his heating bills are £80 a month?

The parapet is a part of the design I need really as the cladding runs level all the way round, I don’t want to see the flat roof. I could probably just lay EPDM over the SIP if I were to be able to install it with a fall. I’m wondering if building the roof traditionally would be cheaper though as I could frame it out myself. I don’t believe SIPS is vapour impermeable, the SIP company specify a robust vapour barrier.

I guess there's always more than one way to skin a cat, are you suggesting some sort of fan to blow air through the vented cavity?

I'm thinking maybe I would be better looking at a warm roof as it appears to be lots of cold bridges with the supporting timbers

Basically the overall height is supposed to be 3m maximum (as stated by the permission). If I move to a warm roof this will need to be increased to 3150-3200mm Steel isn't in place, basically we're only just out of the ground. Trying to finalise the drawings from the SIP suppliers. The drawing you have referenced is their one, even if I used the batons and ply as they suggest I'm guessing I'd have to bring this void up the parapet and exit under the coping strip to allow ventilation?

Looking for a bit of guidance on the flat rood=f of our kitchen extension. Our rear extension is underway, we decided to go with SIP's and it was to be the full envelope. Roof, walls just bosh it up and off you go. The SIP supplier has doubts about the flat roof, they want to ensure that there is a fully ventilated cavity and now want to change the construction to a warm roof. At this point I must admit that I have done all the design drawings and naively had not considered this to be a cold roof and the intricacies of this system. I don't have an overall section of the roof build up but basically the build up (from inside to ou) is- Plasterboard, SIP, Firing, 18mm OSB, EPDM. It's to have a parapet running all the way round and this is the reason that makes me think I've gone completely down the wrong track, I don't see how this roof can be ventilated. Any advice would be greatly appreciated.

it's pretty hard to see as the scale is quite small but I do have a 25mm PIR up-stand at the edge of the screed. I Guess I could bring the 50mm EPS/PIR up to/slightly higher than the sole plate. I haven't had any design drawings back from SIPCO yet but their standards don't show anything to insulate sole plates. I did wonder how these work in reality, you have a nicely insulated SIP panel just nailed to a pice of timber which is fixed to an existing outer wall. Even if you we're building an entire new build out of SIP's you would have lots of similar details like this at corner junctions and window reveals etc so I didn't think the sole plate would be a massive cold bridge. In fact, do I really need to use a Marmox block?!?

@Redbeard thanks for replying. There's 50mm EPS/PIR up to the Marmox black. It's un-dimensioned currently though

Hi Would be grateful for any feedback on these details. It's for my own extension, first time doing building detailing etc so if there are any schoolboy errors please let me know. The build is for a SIPS extension, I know it's probably very light but the proximity of neighbours tree means I've had to go deeper than standard. I've attempted to design out any thermal bridges, hence the use of a Marmox Thermoblock....hopefully this will mitigate any danger of condensation on the sole plate that I've read about. Thanks for the help in advance!

I get that, I guess the point I was making is why ignore the U value of a door but not windows. So is the insulation internal? If so I assume it’s custom made. I haven’t actually searched but I didn’t think wood was a terrible insulator, they seem to use it on windows frequently.

Sorry if I’m going over old ground, I did do a search but didn’t come up with anything conclusive so…. I’m looking to replace the street door, my wife particularly likes the doors by a company called Gileta who do some very nice designs with triple glazed stained glass. I must admit I haven’t seen a composite as attractive without paying a small fortune. The question is, will a solid wood door & frame be much much worse/colder than a composite one (providing it’s all well sealed and draught free)?. I did read a post where someone was suggesting that its such a small percentage of the exterior wall that U value isn’t important as long as it was draught free, if this is the case though then why bother with triple glazed windows? We’re looking to have a door with a window either side to maximise light as the passage is quite dark. I’m planning on making everything in the renovation as efficient as possible whilst working to a budget.

Thank you for the feedback @Onoff & @Iceverge, I’ve done a bit of research and am thinking of using insulated plasterboard to negate the cold bridge from the existing external wall into the new extension (Blue line on plan). Also regarding the existing house, when replacing the windows I was going to add cavity closers and insulated plasterboard for the internal reveals as per @Onoff suggested. I’m also thinking I need to do something on the ground floor where the rear extension interfaces the existing building. I’m not a huge fan of the standard detail supplied by the SIPs company for interfacing/connecting to an existing wall. It’s just a timber baton/sole plate with a DPM that the sip panel is screwed to. It’s an obviously a cold bridge. Although I guess it’s not in their remit to detail this kind of thing out.

@Iceverge thanks for the feedback. I’d be most interested in hearing solutions to the thermal bridge problems, or even just explain to me where they are (I’m assuming the junction between existing wall and SIPs panel for a start). I’m not gong for passive standards…probably nowhere near tbh. But, I would like to make it as efficient as possible and potentially get the bills down (or just stop them going up!) The detailing and extra work I’m doing on the drawings will hopefully mitigate some of these problems. Maybe the SIP supplier will advise? Although I rather suspect they will be more interested in banging it out as quick as possible. As for wrapping the whole house…I’d consider it but the local authority wouldn’t. It was an ache in the balls getting permission for the extensions let alone changing the appearance of the house.

No not yet, these drawings were submitted to the SIP supplier and they produce all the relevant building control drawings.

I have some drawings, still a work in progress whilst I try to iron out details/decide which way to go… I have known the builder since uni so he’s a very old friend. Which is why I’m not just dismissing his pessimism out of hand, had lots of people warn me off of ASHP but none ever had any real world experience….one even went on to have one fitted himself, by his plumber whom I’m sure probably over-specced as they generally do with a combi