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ADLIan

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Everything posted by ADLIan

  1. ADLIan
    Good news. However that calculation is not in line with BS 6229 on flat roofing which uses more extreme external conditions (as my message above). Internal humidity class may need stepping up (dwelling with high occupancy) to cover worst case scenario
  2. ADLIan
    Normally there would not be any additional insulation between the roof joists. If adding something for acoustics keep it low density/higher conductivity mineral wool and ask the flat roof insulation manufacturer to run the CRA with specific reference to BS 6229. Ensure the AVCL above the plasterboard is as 'fully sealed' as possible, it will never be perfect!
  3. ADLIan
    I doubt you'd get the insulation manufacturers to support the use of hybrid flat roof. Not covered in Appr Docs or BS on condensation risk. BS on flat roofing mentions hybrid roofs but warns against their use requiring full CRA, under specific climatic conditions, and very careful detailing of the air & vapour control layer, it must be 'fully sealed' (not sure how you achieve that in practice!)
  4. ADLIan
    The parapet roof/wall junction you refer to is from the Scottish ACDs. (It is not very detail in one sense in that it is showing a hybrid warm roof construction which is generally not recommended). Note it has a layer of insulation internal to the TF (not just between). If you have this construction then download the Scottish ACDs as all the psi-values will be much better. Note also limitations/constraints on rest of construction.
  5. ADLIan
    @Moonshine That document (SAP OCDEA nher) is out of date but does give good info on TBs. Download latest SAP conventions (Sept 19) from the BRE SAP website for current advice.
  6. ADLIan
    Difficult to tell. TER looks to be in the right ballpark for gas fired heating. Read the SAP document carefully as most answers are in there. Possible errors are air infiltration rate, treatment of linear thermal bridges, thermal mass, boiler efficiency, heating controls...I’ve not used the Stroma software for a long time but would imagine it would give an error message for anything totally out of step with SAP.
  7. ADLIan
    The use of a vcl is shown in relevant Bldg Reg Approved Doc & British Standard (and I believe timber frame guidance from TRADA)
  8. ADLIan
    Existing house, even if extended or planned extension, would have SAP energy rating EPC done by domestic energy assessor (DEA) using rdSAP. On construction (OCDEA) SAP assessor (for design stage/as built SAP) would not normally get involved in this instance. May need rdSAPassessment before and after extension. Different skill sets and different accreditation schemes for full SAP and rdSAP.
  9. ADLIan
    What value was assumed at the design stage SAP assessment to show Part L1A compliance? This, or better, will be your target for the test.
  10. ADLIan
    Air pressure test can be avoided for a single house but the SAP assessment must use the default air infiltration rate of 15 - unless accounted for at the design stage this will probably result in Building Reg failure (CO2 emissions and fabric efficiency). Compare this value to some of the numbers achieved by members on here of 3 or lower! I regularly see values of about 7 with masonry construction and standard levels of workmanship/detailing.
  11. ADLIan
    I’m aware of that. My reply was more in connection with why use a 100kg/m3 slab when there is no need to. Assuming pricing is linked to density there are probably more cost effective solutions.
  12. ADLIan
    For acoustic insulation denser does not equal better - at normal, commercial densities, they all do the same job. Bldg Regs need 100mm thickness at 10kg/m3 as minimum, denser will be more expensive but acoustics will be the same (the ceiling, floor finish and effect of joists has a bigger impact).
  13. ADLIan
    I wouldn't use 032 mineral wool between timber studs. Will give little to U-value but at much more cost, 035 product will be OK.
  14. ADLIan
    The U-value table from Black Mountain is meaningless. U-values apply to the whole build up, including all individual elements, of the floor, wall or roof. Additionally with timber frame it does not account for 15% thermal bridging of the insulation - the Kingspan figure does. Looking at insulation in isolation the hemp has a thermal conductivity of 0.039 W/mK compared to 0.018 (?) W/mK for Kingspan. The simple ratio of these 2 values shows you need twice the thickness of hemp to equate to the Kingspan product. Mineral wool is normally the product of choice here for ease of use and robustness of install, has good 'eco' credential and not oil based.
  15. ADLIan
    Fire!! EPS will soften/melt, plaster will delaminate leaving eps exposed to add to the fire load. Mechanically fixed metal mesh as carrier may be an answer.
  16. ADLIan
    Do not render on insulation on timber frame. Render should be on carrier board with vent cavity behind. See Bldg Regs and any good document on TF construction (see STA or TRADA guidelines). Wood fibre manufacturers guidance should not be relied on. Some did have BBA certs covering direct render but these all appear to have been withdrawn.
  17. ADLIan
    Have you a photo showing the front elevation of this bump out rather than the side. If only a porch and the main external door is between the house and this area then it’s probably outside the thermal envelope so no insulation required. However it looks to be too long for that and may well include part of a ground floor room ceiling in which it should be insulated with 300mm (min) of quilt insulation. Looks like they did try to prevent the thermal bridge across the steels by packing with insulation - not sure how successful that would be! Run more insulation vertically against wall to minimise thermal bridge through steel. Not sure how you would do this so late in the day, perhaps have to remove roof tiles. Is house still under any warranty?
  18. ADLIan
    The area weighted average u-value is the way to go however if the main wall/Uval accounts for at least 90% of the total wall area just use that value
  19. ADLIan
    Best practice? Please read MIs, BS and BBA certs, no ply/osb above insulation. Lots of fire safety info on internet re torch on systems. Moving to single ply membranes still no need for ply/osb above insulation (it’s in the wrong place!). Normally rubber/PVC single ply membrane is mech fixed or adhered direct to insulation.
  20. ADLIan
    Your flat roof is a standard detail apart from the extra layer of ply above the insulation - this is not required. Kingspan, and other PUR manufacturers, have insulation that will accept torch-on membranes and it looks like the fixings are OK. Remember the flame is directed at the roll of felt to melt the bitumen layer on it, not onto the insulation. Torch-on systems seem to have lost favour due to fire risk but if appropriate safety measures are taken it is quite acceptable.
  21. ADLIan
    Also EPS, board or beads, is not used for acoustic insulation.
  22. ADLIan
    Difference with a flat roof is the waterproof membrane/layer which invariably has a massively high vapour resistance but is on the cold side of the insulation. This situation should not arise with TF walls.
  23. ADLIan
    @scottishjohnPlease have a look at BR 443 and the various caveats about metal (not discrete screw fixings or wall ties) penetrating an insulation layer. Kingspan composite panels normally sit above the purlins, similarly the insulation division normally show the insulation external to purlins/deck or light steel frame studs. @moldyProblem with a compressible insulation is that it's insulation value will depend upon its compressed thickness! Simple solution is to use the loft legs that are designed for this application.
  24. ADLIan
    The Actis claim of being equivalent to over 200mm of mineral wool was demolished many years ago. If I remember correctly it was back in 2006 when new guidance in support of the Building Regs was issued.
  25. ADLIan
    18 or 22mm of ply/OSB will do little to protect the top flange. Please accept the fact that metal penetrating an insulation layer really does ‘degrade’ the overall thermal thermal performance of this layer considerably. I’ve done plenty of 2D and 3D thermal modelling showing the effect. Have a look at heat losses thru steel stud walls and rain screen cladding systems
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