External Wrap Insulation seals the surface of a house in a seamless envelope that could bring 30% energy savings, says Kya deLongchamps.
External wrap insulation (EWI) or External thermal insulating composite systems (ETICS) neatly dubbed ‘the wrap’ is a serious spend in retrofit.
Even with generous improvements to the SEAI Better Homes scheme of up to €6,000 grant assistance, chances are you will be putting another 200% of that grant allowance number back into the pot and working back through the Home Renovation Incentive Scheme to recover at least some of the 13.5% Vat.
We asked Tom Halpin, and the technical team at the SEAI about grant-aided uptake in EWI.
“So far, just over 200,000 homes have had energy efficiency upgrades grant-aided through the Better Energy Homes scheme of which 15,900 (or 8%) undertook external wall insulation.
“This is on top of the 112,000 who did cavity wall insulation and 12,700 who did dry-lining. People generally opt for the lower cost option which is suitable for their home, even though EWI may result in a superior overall result. This tallies with our research which, unsurprisingly, shows that homeowner willingness to invest, declines as the cost of works increases.”
Still, taking EWI to a whole house envelope, the payback on a draughty house costing thousands of euro in oil or natural gas despite a modern condensing boiler, could be in the range of a 30%. That’s a massive reduction of a heating bill in many instances. A 15-year return to the black on a €15,000 investment (before grant and HRI aid) is highly credible.
This sounds like a very long time. Still, the comfort enjoyed in the house, the elimination of damp and fungus issues and an increase in the improvement in the building’s kerb appeal can throw this blunt financial pay-back into a brighter perspective.
Additional positives with EWI are a reduction in airborne noise through the walls and the weather resistance of a tough, new skin for your home.
EWI has a large positive percentage results in fuel energy savings, and with a structurally sound house built before 2006, there’s the potential to bring the U value readings for the walls to the ideal U value of .03.
Given the correct ventilation, extensive EWI instantly increases sensory comfort with reinvigorated ‘warm’ walls, and delivers a complete or partial visual face-lift to the house.
EWI can be applied to solid block and brick walls, and cavity walls (after fill). Though less usually, there are solutions to keep ‘breathing’ old solid stone, rubble-fill walls warmer too, with wood fibre or cork boards, dressed in lime renders.
For houses of standard construction, the technology is proven, effective, carries a guarantee, and is relatively easy to understand as a client. EWI can be applied to part or the whole of a building 150mm over ground level, and the cheapest way to include it is when other serious work is being executed during a more holistic, whole-house renovation.
This is clearly a good time to get the attic insulation in order and, where cavity walls exist, they should be filled with foam or beads to allow EWI to work effectively. There’s little point beefing up the walls, if there’s pernicious rising damp and your double glazed units and doors are failing.
So what’s the process? With EWI, the entire exterior surfacing of wall of the house, plinth to eaves (bar window and door reveals) is wrapped in a seamless ‘blanket’ of insulation.
First, a layer of generally 100mm thick insulation board is fixed to the walls. A wire or glass fibre fabric reinforcing mesh is set over these boards and the whole lot is covered with dedicated exterior plaster which receives a decorative self-coloured top coat, so you won’t have to paint it.
The finished depth will be anywhere between 150mm and 200mm, noticeably deeper in some instances.
Different composite systems are offered, so shop around for a product and installer with a current NSAI Agrement certificate to ensure they are competent and that the products comply with the Building Regulations. Do a search by product name, by manufacturer, or by certificate number — nsai.ie.
This continuous, three-layer solution addresses many of the difficulties surrounding interior insulation and dealing with problem areas such as window and conduits. EWI kills cold-bridging problems where cold ‘jumps’ from one material across to another to enter the house. It looks exactly like traditional crisp render when applied.
What’s exciting about EWI is how it influences the way masonry walls behave. Once cavity walling has been filled and the EWI applied, block walls do what block walls do well — they act as heat stores, taking up some of the ambient heat in the room from passive gain through the windows, radiators, UFH and even body heat.
The walls now store this heat and release it back to the indoor environment instead of (as formerly) conducting it outside. The walls are now warmer to the touch, reducing the potential for condensation indoors too. The work should take about two weeks and generally no planning permission is required.
Having the work conducted outside, there’s relatively light disruption on site, and no ingress on your floor space by thickening up walls, indoors. This new EWI when finished should be all but airtight, and therefore (build tight, ventilate right), mechanical ventilation measures should be taken, if needed, to ensure safe, regular, exchanges of fresh air indoors.
Window reveals will require special attention as obviously adding 200mm of insulation across your view all round simply won’t work. Some homes with skinny cills and roof profiles with shallow eaves may be unsuited to EWI as the measures to bring the competing surfaces to a comfortable marriage could take the costs beyond economic. Talk to your engineer and supplier about particular, proven solutions to these standard problems. EWI may not be right for your home at all.
Every project should be carefully assessed on its own merits, the available, cheaper alternatives (including internal insulation) and the wider financial landscape - €100/m2 - €125/m2 is commonly cited as the cost for EWI in Ireland, but consider this a starting point.
There may be ancillary costs like ventilation improvements, the cost of hiring scaffolding and issues around moving exterior waste, sub-floor vents, utility pipes and cables fixed to the walls. Adequate background insulation may require further expense, but with the increase to air-tightness, it’s crucial to get readings done by your supplier or an independent specialist.
Get bids for the work from multiple reputable firms registered with the SEAI (site visits should be free). Ensure you know exactly what your quote is for, including any nebulous provisional costings (PCs) and how long the work will take. Can the firm take on extra projects such as lingering structural problems and loft insulation?
Wrap yourself up in a binding contract. Your supplier and installer will be on the SEAI register if you’re planning on receiving grant aid or HRI help, NSA registered and so on, but you still need that contract in hand. The best reference you can get is from someone who has had work done recently who is willing to vouch for the firm.
- For more information on EWI download this PDF file from the NSAI: https://www.nsai.ie/Our-Services-(1)/Agrement/Homeowner-Info/ETICS-Homeowner-Info-Leaflet_Final.aspx
The fire that claimed 72 lives in Grenfell Tower London involved a building with external panels. They were what is termed cassette rain-screen panels which feature (crucially) a ventilation gap, rather than solid external insulation panels used for domestic buildings.
These type of panels make up a solid panel bonded directly to the wall. The insulation layer is of limited combustibility or non-combustible and will not, when properly installed, start or accelerate a fire. Any cladding is meant to be installed so that it prevents fire running across the building or jumping from window to window, or in terraces and flats, from property to property.
Ask your supplier/ installer for more details. National Standards Authority of Ireland-approved products comply with all building regulations. The Sustainable Energy Authority of Ireland technical team says: “A registered gas installer installer is required for moving gas pipes downstream of the meter, extending flues, boiler condensation pipes, etc. The ESB may also be required should there be overhead lines or external services.”
- Generally your local authority does not need to know about EWI, but it can fall foul of council guidelines. If you’re not sure, ask the local planning office who will tell you what further details (if any) they need, citizensinformation.ie.
- Where electricity wires or cables are attached to external walls or soffits you must contact ESB Networks well in advance of the works commencing in order to arrange for the required alteration — nsai.ie. Tel: 1850 372 757.
- For houses with natural gas installations, Bord Gáis Networks must be contacted. They will then provide the necessary assistance to either move the meter box to a suitable alternative location or temporarily remove and then refit the meter box on completion of the works. Tel: 1850 200694.
- It is good manners to let close neighbours know of the comings and goings of crews during the couple of weeks it takes to complete a typical EWI installation (without hitches). Try to minimise noise before and after business hours and avoid blocking access during the works.
- A BER after the completion of works will be mandatory from the SEAI.
- If you don’t know a thing about EWI, have concerns and have the money to do it, appoint a project manager to act on your behalf. Many local consultant engineering firms offer these services.