ADLIan

PeterW - problem with blown bead (or fibre) is you never know if the cavity is filled correctly and without voids - the estimate of product usage and target installed density is VERY approximate. This may be OK with refurb where anything is better than nothng but not, in my view, in new build. At least with a built in product you can see if it's installed correctly or not! Ian

Hi ProDave It's not just BC sign off - the wall has got to last long after your BC has lost interest. The recomendation from TRADA etc is there for a reason. From past experience they note this type of system causes problems in the longer term - if you are happy to accept this risk then fine. I note that a woodfibre product, Diffutherm, had BBA certification for your exact application but it has now lapsed or been withdrawn. Ian

Sorry been awol on trans atlantic flight! Nice pic Jack. I've seen similar with polyurethane and gaps of several cm between the slabs! Back to the main topic. Generally no need to vent the cavity on standard masonry cavity or TF with brick/block cladding (though weep holes will allow some vent this is not the primary aim of these gizmos). Extra insulation can be applied external to the TF studs but the render should not be applied directly to this. With render finish on timber frame there should be a vented and drained cavity behind the render system (and carrier board or mesh) but in front of the extra insulation. The performance of the insulation will not be affected in this instance. Sorry ProDave but I do not see any meaningfull approval, i.e. BBA or similar, on the link and your detail is not supported by TRADA (see Timber Frame Construction, 5th Ed), NHBC Standards or Building Regs. The fact that BC accepted it may simply mean a lack of undertsanding here. It is not a condensation issue but an issue with rain/moisture penetrating the render system and then having ready access to timber and wood based materials - the drained/vented cavity avoids this problem and is shown by the mainstream insulation manufacturers in TF systems. Ian

ProDave - is that an accepted detail? TRADA always show a ventilated cavity behind the render system - I believe this is to avoid moisture transmission through the render (& insulation) back into the timber frame.

Check product installation instructions and BBA certificates - due to this being a critical application ALL of the mainstream products, full and partial fill, will be certified. Walls will dry OK without a vented cavity. Due to fire regs the cavity must be sealed around openings and at the top of the cavity. Joe90 - was this a standard masonry cavity wall? type of insulation? I have never heard of cavity wall being vented in this instance. Sub floor vent should be ducted thru cavity. Should fire get into the cavity it is hidden and can spread, particularly dangerous is spread of smoke/fire into the roof space. Again check BBA cert for your cavity insulation. Full fill systems, in conjunction with render finish, can be used in severe exposure aeas if BBA certified.

Nothing to do with stale air or condensation - residual cavity is more linked to preventing driving rain penetration but also gives useful thermal performance, especially if insulation has a bright, foil face. Weep holes not classed as providing vent in this instance. Ian

The cavity in standard masonry cavity construction is not ventilated i.e. it is not provided with gaps/vents to deliberately vent the cavity. Benefit of low emisivity facings on cavity resistance and aircrete blocks externally can therefore be assumed. Correct in that any elements external to a ventiliated cavity are ignored (see BS EN ISO 6946 on U-value calcs). Insulation manufacturers tend to assume brick/dense block outer so contact them for alternative construction U-values. Ian

Scot Regs pretty much reflect English Regs. 100mm mineral wool between joists.

Building Regs require 'mineral wool' (this is glass or stone wool) min 10 kg/m3, 25mm (min) in partitions and 100mm (min) in intermediate floors. Density in walls is normally higher to give product mechanical strength for vertical use. Do not go too dense (more than approx 25-30 kg/m3?) as it's a waste of money. Warmcell is not included as generic BR solution so you would need indepependent test data for use in wall and floor of the same construction.

Knauf Earthwool is glasswool! +1 Declan52

Remember this includes exsiitng builds too. The EPC band D requirement ensures existing housing has reasonable(?) levels of insulation/energy conservation measures before installing the PV. New build will normally be Band B or better.

+1 Just had a look at the EST website section on FITS. Application date & EPC determines the rate of FIT. Lower rate from 10 May

In new build the EPC cannot be produced until the house is 'physically complete' - this includes commisioning of services, air pressure test (if done), confirmation of the 'as built' specfication, use of ACDs etc. So the EPC will ALWAYS be dated after all of the above! I normally receive a copy of the MCS cert for the PV (if available) and provided I have the above will produce the EPC. This has never been a problem in the past in then applying for FIT Suggest you mention this to your supply co.

Hi ProDave Sorry but I do not have the docs refered to. From memory a lot was common sense! No/minimal hot works, no smoking site, site security against arson, sensible/separate storage of combustible materials (polystyrene or similar insulation), ongoing checks and inspections to look for potential problem areas, emergency escape routes/plan, site fire safety plan keep a tidy site. Sorry can only manage 8 of the 16! A quick google however gives this - hope the link works. http://regions.aps.org.uk/visageimages/Documents/PDFs/regional_cpd/Northern_England/16_steps_to_timber_frame_fire_safety.pdf Ian

All Certainly not a trivial or petty issue. Accidental fires (arson, bad practice or pure accident) in part complete TF buildings have been a problem for some time and recognised by TRADA and UKTFA (now Structural Timber Association, STA). All brought to a head in 2006 with a fire in a built-up area of N London involving a part complete 6 storey TF building. In 2008, the UKTFA, in consultation with fire brigade and HSE released the '16 Step to Fire Safety' book which in turn was adopted as official guidance by the HSE. Aimed at larger schemes rather than single dwellings there is the guide, the 'SiteSafe' practices guidance and a registration scheme for projects over 2500m2 total floor area. Unfortunately all this guidance looks to be available to UKTFA/STA members only (see STA website). I'm not a member but was involved in some of the fire testing for different types of TF panel. ian

Glass wool available in high density rolls (0.035/0.032 W/mK) and slabs for TF walls both at 570mm width. Ian

If it's conversion then simple elemental U-values, heating efficiencies etc in Part L1B. No need for DER/TER or DFEE/TFEE or pressure testing but SAP calc is required to generate the EPC on completion. Must be done by on construction energy assessor using full SAP (as its a Reg requirement) rather than RDSAP. Ian

+1 JSH & Declan52 200mm dense mineral wool (0.035 W/mK) underdrawn with 25mm PUR should give approx U=0.16 W/m2K (rafters at 600mm c/c). Use 30mm PUR if rafters at 400mm c/c. Ian

Thansk JSH. A bit of history - the original Actis tests were done on 2 identical 'chalets', from memory in Limoges, France. This info may still be available on the internet somewhere. One chalet had 200mm mineral wool quilt in the roof the other Actis multi foil but not much other data on the construction. Actis measured 'heat loss' from the chalets and came to the conclusion that 200mm quilt = 30mm(?) Actis. There was never enough data to check if they were actually measuring heat loss through the roof alone or via a myriad other routes. Complaints to the ASA only resulted in a change of product name, Actis 8, 9, 10......It seems that only when BRE did their work, BR 443 was updated and other manufacturers of multi foil products gained certification using accepted test methods that Actis back tracked. They still use a mixture of in-situ and accpeted testing - not sure how they explain the huge discrepancy. As you say - why trust them now! Hence my warning about thir claimed U-values!

NSS - OK, just looked to be at 400mm c/c looking at 150mm actis between. Check Actis U-vals against their 'certified' thermal values very carefully.

I was involved for many (too many!) years with the ongoing Actis saga and their wild & spurious claims. They now declare thermal performance in accordance with both accepted Standards (EN 12667 and EN 16012) and in-situ/comparative testing (the latter not to be used for U-vals under the Regs). Above roof may only achieve U=0.17 with rafters at 400mm(?) c/c and ventilated airspace above the Actis product and Actis VC product directly under the rafter. Ian