ADLIan

Big problem! Metal rails thru insulation is never a good idea. Top flange will be in cold loft space and will be a major linear thermal bridge (or point thermal bridge if cut into smaller lengths).

Some big pieces of metal penetrating the insulation with above option!

+1 on comments above. Not a very good roof design and the space blanket (multi-foil?) will be doing very little to add to the overall thermal performance. U-value is probably 0.25 W/m2K or even worse.

Dividing the SAP air infiltration rate (at 50 Pa) by 20 gives an approximation for ach in normal conditions. Method above, accounting for volume and exposed area, gives ach still at 50 Pa.

Must use 'Type A' wall ties (lighter with low dynamic stiffness) and minimal fixing density to limit transfer of sound between the 2 leaves. +1 on mortar droppings on ties and bottom of cavity!

Assuming under English Regs Appr Doc E has masonry cavity wall and solid wall options that ‘should’ work but need testing on completion. Alternative is to look at Robust Details (RD) and follow their design details. Unfortunately this only covers new build, not conversion, so testing probably still required unless you can convince BCO otherwise. As above detailing to avoid flanking transmission is critical as is quality of workmanship. Adding mineral wool in the cavity gives little, if any, acoustic benefit as the acoustic performance is down to the mass of the wall and 2 decoupled leaves. Mineral wool rolls or slabs, at least 18 kg/m3, are needed to prevent party cavity wall thermal bypass - a thermal requirement reducing the party wall u-value to zero (See Appr Doc L1). This may not be so critical with conversion work but check with your BCO. The RD view is that this measure must not degrade the acoustic performance of the wall hence they show both filled (optional) and unfilled cavities.

Check with manufacturer - most show short ends fully supported on joists too.

50mm insulation is unlikely to get the required U-value in a ground floor, max allowable is 0.22 W/m2K. Probably requires 80-100mm depending upon footprint. Also I do not think that screed at 12mm thickness is suitable for use directly over insulation. Specialist screed can go down to 40-50mm, sand/cement at least 65mm.

Min. density is 10 kg/m3 - see Section 5.18 of Appr Doc E (same detail in Scotland too). Manufacturers will have suitable products with this spec, see 'acoustic roll' or 'acoustic slabs'.

Conversion work comes under Appr Doc L1B (E&W) with a much more relaxed standard compared to new build. No need for SAP calculation to show compliance as simple elemental U-values are provided. (SAP is needed however to produce the EPC on completion). In basement walls and floors the U-value is dependent upon the basement depth as well as insulation type & thickness, if too difficult to insulate BCO can relax the L1B standard.

Denser does not necessarily equal better. Any mineral wool, min density 10 kg/m3, is deemed to comply with Building Regs here. Problem with acoustics, especially upgrading an existing building or floor. is the issue of flanking transmission short circuiting any benefit from the insulation.

Might well be acceptable in Canada - not necessarily here! No expert on the electrical Regs but do they give any exclusions for particular types of insulation - I doubt it. I'm with you ProDave

The acoustic requirement for internal walls and floors (within dwellings) been in place since early 2000s. For floors the spec is as above and for stud walls basically the same but min thickness of 25mm. Not sure how that quilt will perform acoustically - BCO should have requested test data on floor and wall to show at least 40dB achieved

Not sure that this product is certified for use as an acoustic insulation. Building Regs require mineral (glass or rock) wool, min 100mm thick and min 10 kg/m3 density in this application. Other option is that the quilt manufacturer has a sound test result confirming the floor achieves 40 dB (for new build, if this a yardstick for your requirement).

Barn conversion is a world of difference compared to new build, should have mentioned this at the start. DER/TER and DFEE/TFEE do not apply and defaults for linear thermal bridge and air pressure test are correct. This report is not required for barn conversion (hence confusion in this thread) as required elemental u-values etc are listed in Appr Doc L1B, not L1A. Only use of SAP in this instance is to generate the EPC on completion.

Use of oil does not help due to CO2 emissions. Also, unless instructed to do so, the assessor has been very lazy in adopting the default values for linear thermal bridging (2a) and no air leakage test (3). The detailed analysis of the linear thermal bridging is time consuming (=costly) but something I always do as the default y-value of 15 is a real pain to overcome. Similarly not doing the air pressure test is false economy. There are a couple of other items open to question but without more detail I cannot comment.

I'll post this reply here as it's the most recent but it does overlap with a couple of other threads. The previous Appr Doc L1A was the 2010 version, effective Oct 2010 and included the DER/TER measure (based on CO2 emissions). The next revision was the 2013 version, effective April 2014. This gave an average decrease in CO2 emissions of 6% compared to 2010 but also introduced the Fabric Energy Efficiency Standard, partly to plug a loophole in the 2010 version.The 2016 revision did not contain any technical updates. Not sure of the source of Table 1 above (shown in full in the other thread) but it is riddled with errors. See the original in Appr Doc L1A. These figures are not cast in stone, SAP gives a lot of design flexibility and it is possible to build a wall with 100mm cavity or U=0.28 and still get overall compliance (though not sure why anyone would build a wall with such a poor U-value!). Zero carbon homes by 2016 was a Govt ambition but was kicked into the long grass a few years ago. As regards the EPC Building Control only need this as part of the sign off - it is not part of the compliance paperwork, there is no pass or fail here.

Assuming you only want to comply with the Regs check the required U-value with your SAP assessor (for new build) as SAP gives a lot of design flexibility. The 0.18 mentioned in the Regs is not cast in stone. For better than Regs you may have to increase the cavity to 125mm or 150mm, or even wider, depending upon block and insulation. I'm not a fan of injected cavity wall insulation in new build as there is no way of checking for the presence of voids. At least with built in products you can see any problems and correct them. The 'clear' cavity in cavity walls has nothing to do with condensation issues, it is to minimise the risk of rain penetration. Most insulation products for this application, partial and full fill, are BBA approved as required by the Regs.

That's why I'd suggest getting chapter and verse from your BCO as he's the guy that enforces the Regs. If he's relaxed about this then you may be disappointed by the acoustic performance of your wall, perhaps have a look at the some of the solutions in Part E and adopt some of these measures.

But that new stud wall will add little in the way of acoustic insulation . I would expect double layer of plasterboard (to add mass) and mineral wool between the studs (as an acoustic absorption material). Perhaps check exactly what standard of thermal and acoustic insulation, with numbers, your BCO is asking for.

Your BCO needs to go back to building school. PUR is no good for sound insulation - must be mineral wool between the studs for acoustics. There will also be a thermal requirement for this wall if the other side is an unheated space.

Ed. Read the BS you refer to (there is a more recent version) for surface and airspace resistances and their definitions - values are tabulated but calculation methods also shown. As far as I am aware BRE Digest 108 was withdrawn many years ago (I remember using it at college), the basic principles still apply however but some of the values have changed.

Jeremy - couple of numbers transposed in the BS EN number should be 6946. Also probably easier to remember that an airspace of between 25-300mm, horizontal heat flow and high emissivity surfaces each side (covers most airspaces you're likely to encounter) has a resistance of 0.18 m2K/W. Will be slightly lower for smaller airspaces. Ed - the surface resistances only apply to inner and outer most surfaces of the wall (or roof, floor etc) and are not included in an airspace resistance. Andy - a low emissivity surface does make a BIG difference to the airspace resistance - Ecotherm number looks correct. It will also affect the surface resistances but it is not often that you have low emissivity surfaces internally and/or externally in standard construction. Question to ask is does the Low E, bright, shiny surface stay bright and shiny in the long term!

No need to do the calculation as there is an alternative fittings based approach in Table 2.1 of Appr Doc G - comply with this and all is OK!

Because house is now all 'electric'. SAP rating is based on energy cost. Electricity as main 'heating' fuel is expensive so SAP rating suffers. Electricity has high embodied CO2 (from legacy coal fired power stations - will change in next version of SAP) so CO2 emissions will be higher. Efficiency of ASHP counters the above to some degree. Heat pumps in general make compliance with the Regs easy.