Yet Another Condensation on Internal Wall...

FreeBear

creztor said:  I looked at EPS and XPS. Settled on EPs due to price but also R difference seemed too little. I just looked up PU panels and they cost 5 times what my EPS cost for same thickness. However, I see the higher R rating for PU. 10mm of PU is what I paid for 50mm of EPS. Id have to do some homework but then due to where I live I doubt anyone selling retail would stock it. After this room I'll definitely look into it. Would 10mm of PU provide sane R rating insulation as 50mm if EPS? I'll look into it. Thanks.

Some quick prices from a local builders merchant (all 2.4m x 1.2m) -

50mm EPS £14.40

50mm PIR £31.20

62.5mm insulated PB £55.20

50mm Earthwool batts £32.40 for 6.55m² - Works out at around £14.25 for a 2.4m x 1.2m area.

(No discounts applied)

If you were using PUR/PIR boards instead of EPS, you'd only need ~25mm to achieve the same u-Value - If you want thinner, Aerogel is the way to go, but only if you have very deep pockets.. Regardless of the material used, I'd go for a minimum of 50mm to make it worth while.

creztor

I found some info on the R values below. For me 50mm of M grade EPS was £20 for 2.88m2 (m grade so medium quality not best not worst). XPS is £48 and PIR £48 (learnt about this now thanks) and RPU £96. Based on the R values Id only consider PIR or XPS but they are almost 2.5 more expensive than EPS. If I had more money I'd go XPS/PIR but using EPS will allow me to do 3 rooms and whilst not as good R rating they are basically uninsulated now so still a major improvement. 

FreeBear

creztor said: If I had more money I'd go XPS/PIR but using EPS will allow me to do 3 rooms and whilst not as good R rating they are basically uninsulated now so still a major improvement. 

As with most things, insulation is a trade off between cost, space, and savings. We do what we can with the budget available without losing too much floor space with the expectation that it is worth it at the end of the day.

Over here, I should have used 75mm of PIR/PUR boards to exceed the level required by building regulations. But that would have added quite a bit to the cost and mean even more floor space lost in what is a very small room. As it is, other energy saving measures have been used to offset the shortcomings - We do the best we can.

creztor

Second room done. I officially hate doing joints/plastering and my first room was much better. Looks fine but when you get close you can see too much mud on one joint. Otherwise it is great. Room at least 4 degrees warmer than before without any heating and now heats up extremely fast. I purchased R5 pink batts for the ceiling so will finish that before looking at doing the master bedroom. More space in there so will look at normal wool batts and steel stud framing. Will take up 8.5 to10cm depending. To anyone on the fence just do it and save a bunch. Any small cosmetic issues can be fixed later if needed.