S2D2

Here's one that might cause a healthy debate, but I'm having trouble deciding so thought I'd offer it up to the experts. I'm about to board out our loft for light storage on XL Loft legs which leave a 300mm gap above the ceiling joists. The house was built in 1992, so the ceiling joists are only 70mm deep, giving a 370mm void for loft insulation. Currently we have two forms of loft insulation: the original loose fill fibreglass "filling" the 70mm joist depth and approx 170mm of newer (approx 8 years old) fibreglass insulation rolls installed before we moved in under one of the previous energy company schemes. The newer roll is generally in good condition, heavily compressed by the previous owner's loft boards in some places yet should be reusable. The debate I'm having is on whether to replace the loose fill fibreglass insulation which is now 30 years old with new fibreglass rolls. It is heavily compacted across the loft and probably has an average thickness now of ~30-40mm instead of the 70mm it should be filling which will obviously be impacting the R-value and allowing air currents between the two layers of insulation. My options as I see it are as follows: 1) Fluff it up as best as possible, get on with boarding the loft. Save a lot of faff and swearing in a low head height loft space. 2) Redistribute and fluff into half the area, fill the other half with new insulation. Old stuff presumably twice as dense after this, R-value reduced to..? 3) Get rid of all the loose fill and replace with new loft roll (100mm squashed slightly into 70mm, R-value reduced to..?). Sending it to landfill doesn't sit well with me but maybe freecycle could avoid that issue? After relaying the 170mm I'll add new 100mm roll which should give me 340mm insulation and a 30mm air gap below the chipboard, which I've heard some people recommend to avoid condensation issues under the chipboard. Our loft has had severe condensation issues in previous years but that appears to have been fixed by the addition of felt lap vents which have left it dry for a whole year now. To allay any concerns, I'm using a proper fitted/filtered mask, goggles and long clothing. Loose fill fibreglass is the devil when disturbed.

Hi @Marvin, thanks for the great response! By plasterboard tenting I mean we have dot and dab plasterboard, not edge sealed and internal penetrations also not sealed, so we have an air current behind the plasterboard from the cavity and loft. There are probably other names for it as I believe it's a common issue in modern-ish houses where care was not taken during construction. Your post is basically a list of the issues with our house when we moved in and is a great reference for anyone in a similar position. Here's a summary of what I've done around these issues so far: External penetrations sealed around pipes etc. One window frame sealant redone, I need to get round to the rest as they all have gaps Several internal penetrations sealed when possible, tv aerial holes, water main penetration etc. Bathrooms are indeed a pain as I can't get to the pipes due to built in cupboards that were installed before we moved in Intumescent brush seals on integrated garage door to house Flexible expanding foam and sealant applied to all of upstairs junction between chipboard floor and skirting before new carpet was laid Slip layer on floating chipboard floor lapped up behind skirting board when kitchen subfloor was replaced and taped to plasterboard Letterbox replaced for a better sealed version with draft brushes Loft hatch replaced with Manthorpe GL250, old one had no seal whatsoever Chimney sheep and cap fitted to disused chimney Humid/stale air upstairs was indeed a problem, I installed a Nuaire Drimaster PIV system which solved it overnight, the air is much fresher. This is coupled with a trickle extractor in the main bathroom with humidity/switched boost. Felt lap vents fitted in the loft to prevent an annual two-week January phenomenon where condensation would go crazy and effectively rain in the loft Loft lids fitted to downlights in the loft, sealed to plasterboard to allow insulating over Separate thread on loft insulation to come, watch this space!

I'm a long time lurker and very grateful for all the information shared on this forum so thought I should eventually contibute. Sadly self build is not on the table in my area and housing stock variety is also limited. We have an average sized four bed detached house built in the mid 1990s which means we have some insulation on one hand and suffer from plasterboard tenting on the other hand. Newer more insulated housing is available but the compromise on garden space/being overlooked is too high for us. I'll save specific issues/projects for other threads but am mainly interested in improvements for buildings of this era where insulation was barely a consideration and airtightness was ignored. Thanks again to all those sharing their knowledge, it was a great help to previous projects like replacing the kitchen including subfloor.