SteveG40

Understood. Probably didn't mention the slightly laid back attitude our BCO has. With wood fibre, Do you install this as batts up agains the wall? or as some form of infill in a separate stud wall?

To be fair our BCO is quite good (Went private). He just mentions that we 'should' not 'must' and that we would feel benefit from upgrading the walls while the house is in such a state of refurbishment. He actually suggested even if we just chuck 25mm PIR up it's better than nothing (His words!). But I'm looking for perhaps a more educated/thought through view on this. We are re plastering all of the walls anyway so it makes sense to perhaps get something on the walls before we plaster. We are fitting an ASHP so minimising heat loss will all help. I'm not trying to get to passive standards, but something to help with comfort and I'm happy to loose a little space off the room size in doing so.

Hi all First time poster on the forum, although have been a long time lurker. Just looking at getting peoples opinions/advice on what would be the best way forward with our bungalow renovation. Building control came around and noted that we had removed an amount of plaster from a wall. Said wall incidentally has been removed entirely for the installation of a wide sliding door. But the BCO mentioned that really as we had removed the plaster that it triggers us having to thermally upgrade the rest that wall around the new slider. No mention of the other outside walls in that room! But seeings as we are doing so much other work it makes sense to try and improve the outside walls as much as we can. Property is a 1950s block and block (both inner and outer skins medium dense concrete block) Outside skin is painted render in good condition, sadly our eaves overhang is only 75mm to the eaves vent. So I'm thinking EWI is not the best choice with this restriction. Cavity has been filled with Urea Formaldehyde foam insulation in a 65mm cavity. This has been installed possibly as far back as the 1990s or older, but appears in good condition, possible due to the previous owners regular repainting of the render. Costs prohibit removing/refilling this of the time being and so I think I'm looking at the IWI route. Now this opens up a can of worms/confusion when speaking to various insulation suppliers! The PIR boys say cover the walls in PIR laminated plasterboard. Others say that's a bad idea as the full fill nature of the cavities mean that I should treat the wall as if its a solid brick wall and go down the lime, breathable, wood fibre route. It must be noted that all these people are the sellers of products and so will naturally push their own stuff. not necessarily what's best for my house. Searching on the net doesn't bring up much about what I thought was a common construction. I find lots of EWI, or suggesting I fill the cavity with PIR boards which is impossible with the house already built and filled. All information on IWI are largely related to Solid wall construction, rather than improving an existing cavity wall construction. Anybody got any advice on what would be a wise choice going forward? Many thanks Steve

We installed it as per their technical departments recommendations. I contacted them to get a U-value calculation and condensation risk analysis that I could present to the BCO to show that the construction would meet the Building regs requirements. I did have some lengthy phone calls with them searching through various solutions in their database. Most/all of them suggest leaving a 50mm gap between the roof felt and the rear face of the Hybrid. They even demand sealing this gap completely to prevent an airflow (which goes against all general guidance with cold roof installations!) Sealing this void one would assume would only contribute to an increase in temperature in void further accelerating the melting of the glue.

The glue seems pretty poor. Similar to the kiddies melted glue gun type stuff. Very surprised they decided to use glue that softens at such low temperatures. Especially as it's largely used in loft conversions, which get toasty in summertime

We recently used Actis Hybris for renovating a loft conversion. Prior research seemed to suggest it was a far easier and quicker, less nasty dust etc and a lot of professional loft conversion companies preferred it due to the compressibility to successfully seal it between rafters minimising performance gap etc. However, Summertime has showed a massive flaw! We put this in between the rafters, up close (but leaving a gap) to the underside of the roofing slates. The slates being dark in colour absorb tons of heat in the summer sun. This heat is emitted into the back of the Hybris product. This is the 'honeycomb' design product that concertinas out to create lists of little air pockets with foil layers in between. The heat melts the glue that hold this product together and it all falls apart. It has all delaminated and flapping around loose which I would assume throws much of its insulation properties out of the window!