Practical Eco

Toy helps home energy audits

So what's the "Wizard Stick", a child's toy, doing on a site about high performance building?

I have Bill Klotz of EcoAnthracite to thank for this, and I hope he won't mind me giving away this little secret. Anyone doing home energy audits needs to check the seals around doors and windows with a smoke making machine or a wisp of tissue. This helps you identify areas that need attention, weather stripping or sealing. Professional machines cost around $100 or more in most places. This Wizard Stick, on the other hand, costs a mere $16.95 on Amazon, and does the same job.

Even if you're not a professional energy auditor, like Bill , you can easily afford this little gizmo to keep a check on how well sealed your house is, or a neighbor's or a friend's house.

I've also added it to my A-Store for convenience.

Powered Attic Ventillation? Contentious subject.

On my walk around the neighborhood yesterday I saw the biggest roof mounted attive ventillator that I've ever seen - twice as big as the one pictured.  So it's got me thinking about the issue of attic ventillation. 

The sales positioning for these fans is that by ventillating your attic you remove the heat and save money on your air conditioning.  But I've read a respected view from Advanced Energy that refutes this claim.  See the article on Advanced Energy's site here.  They say that since almost all of the heat gain is through radiation that ventillation will do little or nothing to improve that.

I consider Advanced Energy to be an authority on matters like this. They do real field research and testing. The houses they tested were all being depressurised to some extent - that's what mainly causes the risk of flame roll out. And you really want positive pressure in your house, at least here in the South. Positive pressure keeps the house from sucking in impurities.  The attic can also pull your cool air up through the cieling and into the outdoors. So it's very important that a house with powered attic ventillation is thoroughly sealed between the conditioned space and the attic space.

On the other hand, speaking to builders I hear the view that you've got to get rid of the heat that builds up in the attic somehow. Proper ventillation is the only way to do that. One builder tells me that in his own attic he has experienced cooler temperatures since installing a powered ventillator.  Also I found a very detailed report here from the Florida Solar Energy Center that explores the issue well and comes down in favor of powered ventillation.

It's obviously a complex issue with no simple answers.  If building from scratch or if you can afford it, I'd seriously consider spray-foam insulation and sealing the attic - especially if your ducts run in the attic space. For an existing house with ducts in the crawl space, I'd first make sure the attic floor was well sealed from the cieling below so that air isn't exchanged. Then I'd insulate well. Then I'd possibly consider a powered attic ventillation system last. 

The itsy bitsy green kit-home

Anyone not yet ready to build a green home of their own can now buy a miniature house with working solar panels, wind mill, green house and desalination system.  The Power House is available for $149.95 from science-kit distributor Thames & Kosmos. The kit aims to teach children what it’s like to live off the grid.

Power House includes a 96-page full color manual with 70 experiments and 20 building projects. The manual is not just a set of instructions. It is based on a story of a group of high-tech pioneers on an island who must live sustainably with only the resources available to them. As you read their journal entries and learn of their projects and experiments, you build models of the same projects and conduct the same experiments alongside them.  The experiments and projects mimic the tasks the kit’s fictional pioneers must perform.

powers of ten

This may be a little "off-piste" but Treehugger ran an item titled "The Power of the Power of Ten" which I enjoyed because I got to see this wonderful Eames film once again. Who out there HASN'T seen The Power of Ten film by Charles and Ray Eames? It was often played in school when I was young and I saw it twice, but many years ago. Whether you have or have not it's only 10 minutes long and worth viewing. Not least because the Eames' were such a dynamic couple to have been film makers, furniture designers, architects and so much.  Refreshing my memory on the Wikipedia article about Charles, I couldn't help but notice that he gave his daughter the same first name we gave ours - Lucia. I love little meaningless coincidences.

Ethanol from trees?

Right here at NC State researchers are working on ways to genetically modify trees so as to make them a more viable source of cellulose from which to make ethanol.

Dr Vincent Chiang received, last year, a grant from the Department of Energy to find a way to make ethanol from trees. It basically involves modifying the genetics to reduce the amount of lignin in trees, thus enabling the cellulose within to be more easily converted to ethanol.

The New York Times carries a well balanced article on the issues.

Or see the original press release from NCSU

Vented Attics?

I've spoken to quite a few homeowners recently about insulating attics with spray foam insulation like Icynene.  Many worried about keeping the attics properly ventilated.  Here's another area where the building science has evolved. Particularly here in the South, ventilating attics is not necessarily the right thing to do, as with crawl spaces. And, attic fans are not helping either.

The better thing to do is seal the attic and insulate the roof deck with spray foam. With new construction a radiant barrier like TechShield should also be used.

The basic thinking has been to cool the attic with ventilation. But what we now realize is that almost all of the heat transfer into the attic space is through radiation directly through the roof deck. Vents will do nothing to stop this. And when it's hot and humid outside all vents do is draw humidity into the building envelope.

For a good article on this see "Joe's Top Ten List of Dumb Things to do in the South", on the Building Science website. A great general resource.  And take a look at Arnie Katz's article on this subject at the Advanced Energy site. Another great resource.

New Solar PV material based on Carbon nanotubes

A new process for manufacturing thin film solar panels is being employed by Vanguard Solar Inc. in Sudbury MA.

Vanguard says its process for growing flexible solar material -- using carbon nanotubes -- means that its thin-film material can be manufactured in almost any roll-to-roll printing plant.

By changing the cost structure of producing solar materials, Vanguard officials say they can make solar a much cheaper source of energy for commercial and residential buildings.

See the full story on Mass High Tech. News.

Planting Trees May Do More Harm Than Good

A report published in Science magazine on 23rd December suggests that where fast growing conifer plantations have been planted there is often significant damage to local water supplies.  Sometimes that damage can be long-term reducing local water supplies, and making them saltier and more acidic.

I've long been suspicious of tree planting schemes as a way of supposedly offsetting Carbon emissions.  Wouldn't many of those trees have been planted anyhow? I have too often seen these offsets used as a means of greenwashing a business and easing consciences. Well here's another good reason to steer clear of tree-planting schemes and focus on real measures that genuinely reduce greenhouse gas emissions.   

Read the full story in Science

Researchers develop technique to use dirty silicon for cheaper solar energy

A research team at UC Berkeley has come up with a simple way for solar photovoltaic (PV) cells to be made from cheaper and more readily available low-grade silicon.

As PV becomes more popular the price of pure silicon has been driven up. By switching to cheaper and more common low-grade silicon manufacturers could develop less costly solar panels.

There's still work to be done but this research suggests a potential step change in solar PV cost effectiveness in the near future. Even if it means lower efficiencies I imagine there will be a place in the world for low cost and somewhat less efficient panels. Where sun is plentiful, for instance, and where there are no constraints on size.

Full story