![GBE brainstorm improving u values by substitution](https://greenbuildingencyclopaedia.uk/wp-content/uploads/2016/11/GBE-Brainstorm-ImprovingUvaluesBySubstitution.png)
GBE > Encyclopaedia > Code > Brainstorm > G#13507
Improving U values by Substitution (Brainstorm)
Improving U values by Substitution (Brainstorm)
About:
Improving U values by Substitution
I have attached the window and door junctions I have been trying to detail. It would be very helpful if you could take a look and let me know of any comments.
The single skin wall build up we are using consists of:
- 15 mm plasterboard and skim
- 140 mm blockwork
- 150 mm external insulation
- 15 mm render (to be applied prior to frame installation)
The details are as follows:
- Details A, B & C: Typical window head, sill and jamb details.
- Details D, E, F & G: Door D04 head and jamb details.
- Note: D04 consists of a fixed glazed panel facing the terrace, joined to bifolding doors at 90 degrees by a corner post.
We are using:
- L10 Velfac windows,
- L20 Sunflex bifolding doors (supplied by Velfac)
- M21 Sto external render system.
I have attempted to adapt the manufacturer’s standard cavity wall details to suit our single skin structure.
It is the contractor’s intention to apply the render system prior to installation of the windows/doors due to the lead in times on the windows/doors.
I have highlighted some areas in red which we are concerned about in particular:
- How to avoid cold bridging at the junctions?
We need to ensure an overlap between the external wall insulation and the windows/door frames but unsure of how to fix this to the frame edges, particularly as the frames are to be installed after the render. - The fixings from the frames back to the structure?
Is packing required between the frame and the structure and how close must these sit together to ensure the fixing will work? - Are DPCs required at the window and door thresholds?
Where should these be located?
Wow some complications in there!
I suggest you look at:
M21 External Insulated Render: (Jargon Buster) (Checklist)
- Enviroform Solutions Ltd.
- External Insulated Render edge details. (designed for retrofit but some solutions work in new build too).
- Tab 2 then scroll down to links to:
- Thermo Bead at jambs
- Thermo Trac at ground level
- Thermo Fascia at eaves
- Column cladding between windows at corner
There is also a verge gutter system made my another if needed
- Swifix Ltd.
- For attaching all those everyday things to insulated render
- Satellite dish, gate, name plate, washing line, hanging baskets, etc.
L10 Windows L20 Doors
- Partel IRL and UK (On GBE)
- Compacfoam
- High density polystyrene, thermal break, fixings block, gap fillers
- Iso-Chemic
- Iso Bloco One windows and door perimeter seal to opening
- Thermally Insulating, weathertight window perimeter sealing self-adhesive strips
They should keep you busy for a while.
Assuming they are new to you.
Speak later.
L10 Windows and L20 Doors
- Early timber templates to create openings for late arriving windows is common practice.
- An alternative is permanent sub-frames:
- softwood or hardwood to match the window or door
- made to profile to suit construction and to receive window profile
- full decoration to all surfaces before installation
- built into the wall ad secured as it progresses
- insulated render applied up to it
- windows fitted to the sub-frames later
We are currently not meeting the required Building Regulations U-values on the floor, wall and roof build-ups.
What can be done to get there?
Floor: current proposed construction
- 15 mm floor finish
- 75 mm reinforced screed
- 90 mm Kingspan TF70 Thermafloor insulation PIR
- 150 mm concrete beam and block
Current U value: 0.20
(B Regs requirement 0.13)
We would not be able to change the floor insulation depth easily
but maybe we will need to change the product
Question:
- Is there a pre camber on the beams and if so what is the height to be accommodated (minus deflection under load)?
- Is there a structural topping? What maximum thickness?
- Will you use anti-tickle layer and sand for leveling? What Maximum thickness?
Options:
- Thermofloor is PIR consider replacing with PUR/foil faced/other blowing agent (these may be expensive)
- Reinforced screed is thick, if it could be replaced with thinner component then insulation could be increased in thickness (less labour intensive?)
- http://www.fermacell.co.uk/en/docs/Fermacell_Product_Selector_03.2014_ss.pdf
- http://www.fermacell.co.uk/flooring_1215.php?type=download&getFile=3904&filename=fermacell_FlooringSystems_FC02200069_UK.pdf Page 10
K11/111 RIGID SHEET FLOORING BOARDS:
- Substrate: 150 mm concrete beam and block
- Preparation: structural topping? Thickness?
- Levelling: to make up difference: 165 minus 25 to 37.5 (2 or 3 layers of 12.5) – 120 mm insulation
- Anti-tickle layer and sand for leveling? What Maximum thickness?
- Fermacell levelling compound: Thickness: 10 to 100 mm
- Insulation: (options)
- Extruded hard foam XPS DEO 500 kPA maximum 160 mm.
- Extruded hard foam XPS DEO 300 kPa maximum 120 mm.
- Polystyrene hard foam EPD DEO 150 kPa maximum 90 mm.
- Material: wood fibre reinforced desulferisation gypsum
- Manufacturer: Fermacell, 7 The Priory, Old London Road, Canwell, Sutton Coldfield, B72 5SH
- T 0121 311 3480 F 0121 311 1882
- E info@fermacell.co.uk W www.fermacell.co.uk
- Product Reference: 2 E 22 Fermacell dry flooring element
- Thickness: overall. 2 or 3 layers 12.5 mm 25 to 37.5
- Accessories:
- Floor glue.
- Fermacell levelling Compound.
- Fermacell Joint filler.
- Fermacell countersunk cross slot Screws: 19 mm.
- Fermacell floor perimeter insulation strips.
- Handling & Storage: Refer to manufacturer
Consider insulation under slung the beam and block suspended concrete floor (easy to add without changing details)
P10 Insulation
- Insulate Ltd.
- There is a basement version of their product
- Cellar Insulation Ceiling
Consider composite timber I beam floor with insulation in joist zone (late redesign?)
G20 Timber Structure
Consider ground bearing aerated insulating concrete floor (late redesign?)
E10 Concrete
- Concrete Centre
- Advice and Guidance
- Lightweight and Aerated Concrete
- Agrodome in Holland
- 4 houses (1 visitors centre) floor edge detail (sorry annotation in Dutch)
Floor to wall junction
F30 Accessories in Brick/Block/Stone walling
- Do you need a thermal break in the block wall at floor insulation level to prevent thermal bridges?
- Pittsburgh Corning
- Foamglas Perinsul Perimeter Insulation Thermal break
Walls: current proposed construction
- 5 mm Sto Render
- 150 mm EPS external insulation system and fixing carrier?
- 140 mm Medium density concrete blockwork
- 15 mm plasterboard and skim and fixing void
Current U value: 0.21
(B Regs requirement 0.18)
The foundations are already poured.
We cannot change the blockwork or the insulation thickness of the Sto products
- What prevents changing the blockwork materials to AAC? loadbearing capacity?
- What prevents changing the blockwork materials to Extruded fired clay? Learning new details?
- What prevents changing the Sto insulation thickness?
- Drainage details? Eaves Details? Window/Door Details?
- What prevents changing the insulated render materials?
- From EPS to XPS > PUR > Phenolic > PIR with other manufacturers if needed
- Reducing thickness or improving U value
but could potentially add some internal insulation to the wall build up.
- Replace plasterboard, skim and dabs/rails with insulating plaster
- (with or without thickness change)
- Diasen (Manufacturer)
- Ecological Building Systems Ltd. (Supplier)
- Earth and Cork Insulating plaster/render
- Diathonite Evolution
Would this bring a condensation risk?
M20 Plaster M21 Insulated render M24 Clay based plasters
- Yes, probably, needs a vapour check inside unless you use a hygroscopic moisture transport internal insulating plaster
- hygroscopic moisture transport internal insulating plaster:
- Diasen (manufacturer)
- Ecological Building Systems Ltd. (Supplier)
- Earth and Cork Insulating plaster/render
- Diathonite Evolution should manage moisture for you
- Clay or lime should manage moisture but adds no insulation
K11 Linings
- Ecological Building Systems Ltd.
- Calcium silicate insulation board on moisture permeable ‘adhesive’ and moisture permeable finish
- Calsitherm Climate Board
Wall to roof junction
- Are there any linear thermal bridges to resolve?
Main Roof: current proposed construction
- U value: 0.15
- Roofing slates
- 19 x 38 mm sw battens
- 50 x 38 mm sw counter battens
- 50 mm AIM warm roof system stone wool ‘Rockwool’ overlay board
- Glidevale Protect VP400 Type LR roofing underlay
- 150 mm trussed rafters
- 2 x 75 mm glass fibre ‘earthwool rafter roll’ between trussed rafters
- 12.5 mm plasterboard and skim
- (B.Regs requirement 0.13)
We could potentially put a ‘Kingspan’ insulation in the roof instead of the ‘earthwool’
and as this is not breathable we would then need to add a VCL layer.
- Stone wool and glass fibre are not breathable
- (i.e. Breathing construction) but they are moisture permeable.
- Breathing construction also requires hygroscopicity
- (absorbs moisture vapour from the interstices into the fibre helping it to insulate and releases moisture when conditions are right)
- Stone wool and glass fibre are not hygroscopic but hydrophobic
- (rejects moisture from fibre keeping it in the interstices reducing its capacity to insulate)
- Stone wool and glass fibre both need a vapour check layer always
- Stone wool and glass fibre can be oversized and fit closely to timber sections
- and any moisture in interstices could affect the timbers
Replacing stone wool fibre or glass fibre with PIR or PUR insulation
- Increases thermal resistance, improves U value with same thickness
- Is often cut to size and not resilient enough to enable a tight fit to timbers and remains gappy
- PIR and PUR are vapour resistant and so will concentrate moisture vapour at those gaps at timbers
- PIR and PUR both need a vapour check layer always
Stone wool, glass fibre, PIR and PUR
- offer no decrement delay to solar radiation heat and let heat in easily
- offer resistivity to heat escaping
- let heat in, but do not let it out, it may lead to overheating
Consider: Cellular glass, dense wood fibre, cork board, cellulose fibre flake, recycled newspaper
- Cellular glass not practical in timber frame (expensive)
- Eco Merchant (supplier)
- Dense wood fibre rigid board (above rafters)
- Dense wood fibre flexible batts (between rafters)
- Cork board (at rafter level)
- Pen y Coed (supplier/installer)
- Cellulose fibre flake (at ceiling level) economical
I am sorry to inundate you with information but if you do have any suggestions (which wouldn’t increase the contract costs unduly) they would be gratefully received!
- I am glad you did without it I could not respond in detail
- I know very little about prices so you will need to check out the alternatives
- Do you want the Thicknesses of materials working out for you?
- I have just created a ceiling U value calculator, I could develop it for these applications
© GBE NGS ASWS BrianSpecMan aka Brian Murphy
4th November 2016 – 9th November 2016
Improving U values by Substitution (Brainstorm)
Images:
GBE Brainstorm
gbe-brainstorm-improvinguvaluesbysubstitution PDF 5 Pages
GBE CPD
GBE Links
Zero Carbon Hub G#13351
© GBE NGS ASWS BrianSpecMan aka Brian Murphy
8th November 2016