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ADLIan

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Everything posted by ADLIan

  1. ADLIan
    If windows enlarged the max area of new (& old) windows, door, rooflights should be no more than 25% of the floor area of the dwelling otherwise 'compensating measures' are required. See AD L1B. This could be as simple as convincing BCO that the 3G is better than existing windows or it could be full SAPs A lot will depends upon how clued up your BCO is and how fussy he is! Best to resolve this now.
  2. ADLIan
    Low e foil on pur is often certified by manufacturer, bba or similar. Reflective breather membrane, again certified, can make useful reduction in uvalue for clear cavity and brick outer but little benefit with render on carrier board
  3. ADLIan
    You should get U=0.13. Slightly better lambda for PUR and low emissivity air spaces next to foil faced PUR. Difference between brick outer leaf and render on board only impacts 3rd decimal place so still U=0.13. Your TF supplier may not be using 15% bridging in TF as required under Regs but I still only get U=0.12 at best. Get a U-value calculation from them and post it here for comment
  4. ADLIan
    MIs and BBA certificates for PUR cavity insulation show insulation on inner leaf. Mineral wool full fill can be built with either leaf leading. Leading with outer leaf is better practice.
  5. ADLIan
    Hi all. Just a few comments on this thread. The manufacturer is unlikely to overspec or ask for too many vents as the numbers can easily be checked. Possible loss of credibility & loss of sales. BR Appr Docs (& NHBC) require sub floor vent in both timber and concrete suspended floors. NHBC Standards are more prescriptive with the 2m max spacing. This is a good thing as fewer vents, further apart on one wall, is likely to result in pockets of still air between the vents. Could it be argued that the 450mm from each corner be measured from the internal faces of the wall. As above to avoid pockets of still air at this point if, for example, the nearest vents were 2m away.
  6. ADLIan
    Expensive option for such a small roof. Keep it simple and create the fall in the roof structure using firings
  7. ADLIan
    +1 to the above. Note the damaged foil will adversely affect the lambda value of the foam and will not give a low emisivity surface anymore. The foil does nothing for the fire performance, look at Grenfell.
  8. ADLIan
    Its often simpler and more accurate to get the manufacturers to run these figures for you - only takes a phone call or email. Looking at the calculation (I'm not familiar with the use of this software) I would comment; 1. Corrected/uncorrected - may be correcting the U-value for gaps around the insulation (as per the BS). Not required in this instance as you have 2 layers of insulation and the mineral wool is normally deemed to fully fill between the studs. 2. DP = dew point? Does not seem right in this position if it is.Especially with the inclusion of the AVCL 3. Architect is wrong. No need for an airspace. It will impact the U-value but making it higher! Leaving a 25mm airspace will give a low emissivity airspace with resistance 0.44 m2K/W. Filling this gap with 25mm of mineral wool gives a much higher resistance of 0.025/0.035=0.71 m2K/W Other comments; 1. The airspace between the plasterboard and AVCL is not low emissivity. It is high emissivity with resistance 0.18 m2K/W 2. You do not appear to have accounted for the thermal bridging of the studs in the140mm mineral wool and the battens in the service void
  9. 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
  10. ADLIan
    Requirement for pipe insulation is covered in Appr Doc L1A and the Domestic Building Services Compliance Guide
  11. 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 ......
  12. 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
  13. 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.
  14. 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.
  15. 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’.
  16. 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
  17. 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!
  18. 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!)
  19. 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.
  20. 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.
  21. 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.
  22. ADLIan
    The use of a vcl is shown in relevant Bldg Reg Approved Doc & British Standard (and I believe timber frame guidance from TRADA)
  23. 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.
  24. 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.
  25. 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.
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