Thinking of building a house? The advantages of building a timber frame house over the more standard concrete block method include a shorter construction period but the block method has caught up fast in terms of energy efficiency and airtightne.
Estimated at around 30% of the market share of new housing in Ireland, most timber-frame buildings in Ireland feature an outer masonry or brick façade.
Despite the spin, they are very much a hybrid of block and wood.
The Irish Timber Frame Manufacturer’s Association nicely round it up — in timber frame “the inner load bearing/support wall is replaced by an engineered rigid timber frame structure”.
This is not comparing oranges and apples.
The high building standards and energy efficiency demands of Part L of our regulations apply to all new domestic builds.
Put aside knee-jerk prejudice and see what build type suits you and your project.
There’s a persisting, sentimental attachment to twin wall cavity construction in Ireland.
However, timber frame construction, engineered and built off-site in CAD/CAM-controlled factory conditions, takes one whole step of the build out of the vagaries of the Irish weather, which can otherwise decimate a schedule.
The structural supporting walls of a house, including insulation, factory-fitted membranes, and even the service cavity for wiring and plumbing needs, can be swung into position by crane, followed by the roof trusses, and secured on a pre-prepared slab in as little as seven days.
External windows and doors can go in immediately, external finishes started, and those involved in internal services can get straight to work on the first fix of carpentry, plumbing, and electrics without waiting for walls to emerge block by block.
With more dry materials (less plaster and cement), less wet trade work and drying out time is needed, again slashing time on site. Most timber frame manufacturers will offer a package to bring your house or extension to this weather-tight finish, simplifying budgeting for a whole stage of the build.
However, does this really equate to a faster build or money saved?
Despite reducing labour costs on site, you will have to tack on the several months of lead time while the frame (external walls, internal walls, and roof) is manufactured by your supplier — and timber frame as a highly accurate, quality system build will be comparable or even more expensive than a block build.
Energy efficiency and sustainability
Looking at environmental credentials, timber frame wins hands down.
Using wood sourced from sustainable forests in Ireland, Canada, and Scandinavian, timber has less embodied energy than concrete, with a lighter carbon footprint and, in a prefabricated design, arguably less waste on site.
However, it’s the finished product that counts long-term. Build in block, seal the envelope, hit a great BER, and fit it with sustainable heating/insulation/power- saving features — everyone wins.
The energy performance (heat retention) of walls expressed in ‘U’ values was the clarion call for timber frame, but the block build has risen to meet this challenge, and both build types can surpass not only the building regulations but deliver a house to passive house standard.
You can find a useful description of a block built and timber frame passive build by Cyril Mannion EU Certified Passive House Designer at the Sustainable Energy Authority of Ireland website, seai.ie in their renewable publications section.
The two houses came in too close to call in their wall ‘U’ values at 0.12 w/m²k for the block built and 0.11 w/m²k in timber frame, with block finish, Cyril’s personal winner overall.
If you are interested in a prefabricated system build, Cygnum, based in Lissarda in Cork, are currently the only Irish timber frame company with a closed panel building system certified by the Passivhaus Institute in Germany.
Successful timber frame homes require a continuous moisture permeable membrane to the inside walls and high levels of insulation to deliver the ideal of a sealed, heat- retaining envelope.
The walls of a block house with a cavity of 100mm will be thicker to accommodate the amount of insulation to make this real.
Still, there are stunning advances in lightweight Aercrete block, structural insulated panels (SIP), and external insulation changing the face of both new builds and renovation to bring second-hand block houses to warm new life.
Thick block built walls are deliciously cool in summer. Timber frame homes being substantially lighter, are more reactive to standard radiator fed heating systems, but are said to cool down more quickly than the thermal mass of purely masonry examples.
However, this is misleading, as hefty elements such as stone hearths set at the centre of open plan areas and poured concrete flooring can deliver an additional passive ‘heat store’ for ambient and solar gain in a timber frame house.
There is little argument that concrete is a better sound insulator than bald empty stud partition, and in the case of party walls (between semi-detached and apartment properties) timber frames from the 1970s and 80s can give buyers pause.
The creak of upstairs joists is a moot point, as many concrete homes have timber upper floors too, and just the same noise transmission challenges.
The timber shrinkage cited by the Concrete Federation of Ireland as causing problems in upstairs bathrooms (where tiles could pop off a ply floor) are inherent in any house with a timber upper floor.
Solid concrete upper floors (possible with steel but not timber frame) remain a relative luxury, but worth inclusion if you can afford them in your concrete home.
A structural break included in a timber frame, walls fitted with a sound absorbing quilt, boards or loose-fill will deliver a quiet wall, imperceptible (in most instances) in performance from block.
In second hand homes retro-fits such as double internal plasterboard, can do much to reduce nuisance noise room to room.
Where your home abridges a very busy road, it’s worth considering the more deadening calm of a cavity wall, total-block build.
More information: Irish Timber Frame Manufacturers Association www.itfma.ie and the Irish Concrete Federation www.irishconcrete.ie Sustainable Energy Ireland www.seai.ie Passive House Plus (magazine) www.passivehouseplus.ie
Good practice on site is vital
The marketing of building types can be intense and feelings in the green design community run high when it comes the stand off between concrete and timber suppliers.
A timber-frame house which is well designe and built to building regulations, is as durable as a masonry house and will not collapse in Irish conditions or reflect a lower price on the open market.
Both build types have a 60-year design life and the big issue with timber is rot . Rot requires damp.
A modern timber frame is not only treated for rot and insect infestation, but is shielded from the weather by external cladding and from fire by internal components. Rot creating fungi need 20% moisture content or more to thrive.
The timber used in a modern timber frame house will be below 20%, a percentage that will fall over time with a ventilated, regularly occupied home.
A correct ‘breathing’ wall in a masonry house will carry condensation through the wall to the cavity and finally out to the atmosphere.
Where there are problems with block houses they tend to be complaints surrounding damp (inadequate ventilation) and difficulties in heating and retaining energy, problems addressed by modern insulation.
The end of cold-bridging and the new building regulations mean both both systems rely on good practice on site with skilled labour and trades.
An early study by the Department of the Environment comparing houses by type concluded that problems with timber-frame construction where it did occur was the result of failings on site. — an experienced project manager and crew will have no trouble getting this right first time.
You can hang kitchen cabinets and other cabinetry safely to the nearest vertical stud in a timber frame, and there are fixings to get things into that to the centimetre where needed.
What about fire? Fire stops are included in the frame to prevent fire from easily jumping from one panel to the next, and timber frame is not inherently more likely to burn down — ask your insurance company to confirm this in their quotation process.
Your best defence is a fully-detailed smoke alarm system.
HRI: Unexpected payback
The period to carry out improvements to your home and claim under the Home Renovation Incentive Scheme (HRI) continues until December 31, and Minister for Finance willing, Budget 2016 will carry through this highly positive and popular tax relief.
However, many people do not realise that projects outside of new kitchens and small extensions qualify for the VAT claw back.
Keep in mind that the scheme is not a grant and there’s a relatively long waiting period to take advantage of the savings.
Your tax credit is 13.5% of the qualifying expenditure BEFORE Vat paid to a fully tax compliant contractor, registered for the scheme. It will begin in the year after the work is carried out and paid for.
Many of the lesser mentioned outdoor projects are excellent ways to protect and potentially improve the value of your home.
For instance, driveways and landscaping are covered under the scheme, adventures that might not immediately spring to mind.
If you say, spend €10,000 putting in a paved area for your car and hard landscaping with raised beds and pathways around the base of the house, the saving would be €1,350, and will appear in your tax return the following year (your contractor actually files the claim for you).
Built in wardrobes qualify. If you’re drowning in storage issues, could you share out some units over the upstairs bedrooms?
If you are living in a rural area without a community waste facility, an exhausted concrete septic tank may be making its pungent presence felt.
With registration of tanks to comply with EU codes of practice now obligatory, any failings on inspection could cause a real stink.
Retrofit solutions such as BioPure which uses agitation and pumping technology to get the tank digesting properly as a compliant sewage treatment plant, are covered under the HRI.
The tank repair also may qualify for a grant if your local authority feels remedial steps are needed. Biopuretech.ie.
The HRI relief also covers the replacement of the tank, something easily broaching the qualifying €4,405 minimum spend (before VAT).
* For more information, go to www.revenue.ie
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