Robhan

Thanks. It's quite a big room though at 60 sqm. Do you get any overheating issues on hot days as I know mineral wool has a low decrement delay? A builder friend in the village said he used 140mm SIP + 50 extra PIR on his own recent extension but I'm wondering if that is overkill? By the way we are going to use battened cladding on the outside.

Hi We are building a large garden room 12m x 5m and around 2.5m interior height. We have decided to go with a timber frame build rather than concrete block or SIPS. I'm not sure whether to put mineral wool or PIR between the timbers. I know the u-values of PIR are better but I've also read that you can get gaps and also shrinkage which will negate the benefit. I'd also like a continuous second layer of insulation to decrease thermal bridging and improve overall u values and decrement of delay (keeping the building cool on sunny days). So either a 50m layer of PIR, insulated plasterboard or wood fibre (wood fibre is better for helping with the decrement of delay). Also I've read that insulating the outside of the wall with the 2nd layer - so for example putting the 50mm of wood fibre on the outside of the wall is better for condensation. Is that correct? If so why do people insulate on the inside of a new build? I want to keep costs reasonable and ideally if the wall could be around 30cm width or less - but if a little more that is OK as we have plenty of room. I also need to consider wiring. I'm thinking 100mm of PIR and 50mm wood fibre or 140mm mineral wool and 50mm wood fibre or PIR. I'm not sure about the floor or roof. Does anyone have any opinions/insights they could help me with please? What thickness of each insulation should I use and what is the optimum construction to have a good u value and keep cool on hot days? thanks Rob

Thanks. What's it like in winter? Assume blockwork would stay coolest then in summer?

Thanks. Why don't you like SIPs or PIR?

Hi I've just had permission to build a large garden room 12m x 5m which will form a gym and entertainment room. It needs to be built to building regs due to size. It'll have a small kitchen/bathroom. I've spoken to numerous builders (some I know and some getting quotes) and each seems to suggest the best way to build is either SIPs, Blockwork or a timber frame. I'm not a builder so don't know which to choose. Can anyone advise on the benefits/negatives of each and which might be most cost-effective option please? Other questions: Would you go for an insulated concrete base? and with insulation under the concrete or over it? How do I make sure the floor is strong enough? If it was timber frame or blockwork what insulation would you use - PIR or other? Would you go for a warm roof or cold? Any other major considerations to think of? Thanks Rob