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ADLIan

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Everything posted by ADLIan

  1. ADLIan
    As I predicted. In floors you quickly get into case of diminishing returns with thicker/lower lambda insulation so U value will not improve much. Plus SAP relatively insensitive to changes in elemental U values
  2. ADLIan
    Requirement for pipe insulation is covered in Appr Doc L1A and the Domestic Building Services Compliance Guide
  3. ADLIan
    Go for pur. Only one manufacturer of phenolic so it’s priced accordingly! Difference in U-values will be small (especially in the floor) and should not impact SAP numbers to any degree. Get you SAP assessor to run the numbers. Second quality insulation is seconds for a reason; may not achieve the declared physical properties, may not comply with relevant British Standard, may not be fit for use under the Building Regs ......
  4. ADLIan

    120mm PIR

    ADLIan replied to redtop's topic in Heat Insulation

    It’s not the R value that should compared as this is thickness dependant - 300mm of woodfibre will have a better (higher) thermal resistance (R value) than 120mm of PUR! Comparator is the thermal conductivity (lambda value) as this is an inherent physical property of the material and is not thickness dependant. The U value refers to the total build up of a wall, floor or roof. The U value of insulation alone is meaningless. it must have been costly obtaining wood fibre with 3x the R value of PUR, approx twice the thickness and twice(?) the price
  5. ADLIan
    As above nothing to do with the thickness of the insulation, problem is the screed. Standard sand & cement screed onto insulation should be at least 65mm thick with light mesh reinforcement (or fibre reinforcement mixed in). The kitchen unit legs may have imposed too high a point load on the screed & insulation but this is unlikely.
  6. ADLIan
    +1 @ProDave From BS 5250 vapour resistance of 13mm OSB is approx 7 MNs/g. Compare to vapour resistance of 0.12mm (500g) polyethylene sheet at approx 250 MNs/g. This would be classed as a (A)VCL - the OSB offers little resistance.
  7. ADLIan
    The Standard uses -5 Deg C as external winter temp. Not sure what the other conditions are as I'm not directly involved in this sector. Normally the internal classes are low occupancy dwellings and high occupancy dwellings (there are others but not relevant here). A good PUR manufacturer with experience in flat roofing should have this info and work to this Standard. On the positive side I would imagine the construction would be relatively safe looking at the relative thermal performance of the PUR and mineral wool but proceed with caution! Was the calculation done by the manufacturer? I would expect a product name and reference not just ‘PIR’.
  8. 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
  9. 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!
  10. 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!)
  11. 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.
  12. 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.
  13. 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.
  14. ADLIan
    The use of a vcl is shown in relevant Bldg Reg Approved Doc & British Standard (and I believe timber frame guidance from TRADA)
  15. 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.
  16. 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.
  17. 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.
  18. 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.
  19. 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).
  20. 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.
  21. 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.
  22. 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.
  23. 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.
  24. 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?
  25. 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
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