Diary Of An Eco-Builder

Oak bark sounds like the appropriate insulation for tree house, but we need something better

I've been dreaming of insulation for months, but last week we finally fitted the first pieces into Tree House. Grabbing the opportunity of a dry day between the storms, all hands were on deck - the roof deck - to build the thick layer of insulation between the roof's plywood sheathing and the plastic rainscreen that will support our solar power station. By the end of the day the job was done, and the roof was covered in a bright blue tarpaulin just in time for the next downpour.

Our super-insulated roof is not graced with any of the materials alluded to in my dream: hemp, sheep's wool, cork and recycled newspapers. These are all excellent insulants, but - although cork (the bark of the oak Quercus suber) would perhaps be the most fitting choice for Tree House - our roof and floor are in fact being packed with a synthetic product, Kingspan Insulation rigid phenolic boards (www.insulation.kingspan.com).

The key issue with all insulation is to select the most appropriate material for the task. Bark may be all that a tree needs to protect its living tissues from the extremes of the elements, but our "zero carbon" house needs something more substantial. We have chosen rigid phenolic boards for the roof simply because they keep the heat in (or out) better than any other material on the market.

The most important characteristic of any insulant is its thermal conductivity, so always check the value of this when making comparisons. The thermal conductivity of a material is the rate at which heat flows through it when the temperature on one side is greater than the other. This is standardised as the rate of energy flow (in watts) through one metre of material for one degree difference between inside and outside (in degrees Kelvin - the same scale as Centigrade, but starting at absolute zero). Typical values are 0.034 W/mK for mineral wool, 0.037 W/mK for sheep's wool and 0.022 W/mK for phenolic board. The lower the conductivity, the more effective the insulation.

Beyond this bottom line, there are lots of other issues to consider in choosing insulation, such as the size and shape of the space; moisture and fire risks; and the potential for poor installation to undermine effectiveness. For example, we will be spraying Warmcel 500 recycled newspaper (www.excelfibre.com) into our walls because the nooks and crannies of our "I beam" wall studs would not be adequately filled using only rigid boards.

Synthetic insulation materials have often been dismissed by eco-builders because of the blowing agents used in their manufacture. These were originally ozone-depleting CFCs, subsequently replaced by marginally less nasty HCFCs and HFCs. Happily, Kingspan Insulation now produces all its insulants using pentane, which has minimal impact on either the ozone layer or global warming, and any energy used in manufacture is rapidly off-set by its energy-saving performance once installed.

For advice about the insulation in your walls, wall cavities, floors, loft or roof, see the Energy Saving Trust website (www.est.org.uk) or phone 0845 727 7200.

In years to come, our super-insulated roof will keep us cool in hot summers as well as warm in cold winters, so we should sleep soundly beneath it. With any luck, my dreams will be more peaceful too, with all those giggling right-wing sheep long since chased into the wilderness.

Discover more property articles at Homes and Property
Life and Style
Powdered colors are displayed for sale at a market ahead of the Holi festival in Bhopal, India
techHere's what you need to know about the riotous occasion
Arts and Entertainment
Larry David and Rosie Perez in ‘Fish in the Dark’
theatreReview: Had Fish in the Dark been penned by a civilian it would have barely got a reading, let alone £10m advance sales
News
Details of the self-cleaning coating were published last night in the journal Science
science
News
Approved Food sell products past their sell-by dates at discounted prices
i100
News
Life-changing: Simone de Beauvoir in 1947, two years before she wrote 'The Second Sex', credited as the starting point of second wave feminism
peopleHer seminal feminist polemic, The Second Sex, has been published in short-form to mark International Women's Day
Property search
Property search
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Recruitment Genius: Finance Assistant / Credit Controller

£16000 - £18000 per annum: Recruitment Genius: They are an award-winning digit...

Ashdown Group: Senior VMware Platform Engineer - VMware / SAN / Tier3 DC

£45000 - £55000 per annum + benefits: Ashdown Group: Senior VMware Platform En...

Recruitment Genius: Purchasing Assistant

£10000 - £16000 per annum: Recruitment Genius: A distributor of specialist ele...

Recruitment Genius: Sales Ledger Assistant

£17000 - £19000 per annum: Recruitment Genius: A distributor of specialist ele...

Day In a Page

Homeless Veterans campaign: Donations hit record-breaking £1m target after £300,000 gift from Lloyds Bank

Homeless Veterans campaign

Donations hit record-breaking £1m target after huge gift from Lloyds Bank
Flight MH370 a year on: Lost without a trace – but the search goes on

Lost without a trace

But, a year on, the search continues for Flight MH370
Germany's spymasters left red-faced after thieves break into brand new secret service HQ and steal taps

Germany's spy HQ springs a leak

Thieves break into new €1.5bn complex... to steal taps
International Women's Day 2015: Celebrating the whirlwind wit of Simone de Beauvoir

Whirlwind wit of Simone de Beauvoir

Simone de Beauvoir's seminal feminist polemic, 'The Second Sex', has been published in short-form for International Women's Day
Mark Zuckerberg’s hiring policy might suit him – but it wouldn’t work for me

Mark Zuckerberg’s hiring policy might suit him – but it wouldn’t work for me

Why would I want to employ someone I’d be happy to have as my boss, asks Simon Kelner
Confessions of a planespotter: With three Britons under arrest in the UAE, the perils have never been more apparent

Confessions of a planespotter

With three Britons under arrest in the UAE, the perils have never been more apparent. Sam Masters explains the appeal
Russia's gulag museum 'makes no mention' of Stalin's atrocities

Russia's gulag museum

Ministry of Culture-run site 'makes no mention' of Stalin's atrocities
The big fresh food con: Alarming truth behind the chocolate muffin that won't decay

The big fresh food con

Joanna Blythman reveals the alarming truth behind the chocolate muffin that won't decay
Virginia Ironside was my landlady: What is it like to live with an agony aunt on call 24/7?

Virginia Ironside was my landlady

Tim Willis reveals what it's like to live with an agony aunt on call 24/7
Paris Fashion Week 2015: The wit and wisdom of Manish Arora's exercise in high camp

Paris Fashion Week 2015

The wit and wisdom of Manish Arora's exercise in high camp
8 best workout DVDs

8 best workout DVDs

If your 'New Year new you' regime hasn’t lasted beyond February, why not try working out from home?
Paul Scholes column: I don't believe Jonny Evans was spitting at Papiss Cissé. It was a reflex. But what the Newcastle striker did next was horrible

Paul Scholes column

I don't believe Evans was spitting at Cissé. It was a reflex. But what the Newcastle striker did next was horrible
Miguel Layun interview: From the Azteca to Vicarage Road with a million followers

From the Azteca to Vicarage Road with a million followers

Miguel Layun is a star in Mexico where he was criticised for leaving to join Watford. But he says he sees the bigger picture
Frank Warren column: Amir Khan ready to meet winner of Floyd Mayweather v Manny Pacquiao

Khan ready to meet winner of Mayweather v Pacquiao

The Bolton fighter is unlikely to take on Kell Brook with two superstar opponents on the horizon, says Frank Warren
War with Isis: Iraq's government fights to win back Tikrit from militants - but then what?

Baghdad fights to win back Tikrit from Isis – but then what?

Patrick Cockburn reports from Kirkuk on a conflict which sectarianism has made intractable