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Green Building Priority #6 – Ensure Durability and Reuse Existing Buildings

Number 6 in my list of the top 10 green building priorities is to ensure that the home is durably built or renovated, and to reuse existing buildings when possible rather than building new

Posted on Oct 13 2010 by AlexWilson

A green home should last a long time. Living in a timber-frame home in Dummerston, Vermont that was built in 1785 and having grown up in a log home in Berwyn, Pennsylvania that was built in 1710 (three centuries ago this year), I think a lot about durability. It shocks me to realize that some of the homes being built today are designed for just a fifty-year lifespan. I feel that homes should last a minimum of 500 years. My friend (and leading building science expert) Joe Lstiburek once told me that a well-designed home today should last 1,000 years.

Creating durable homes involves a three-part effort: the first is designing it right with proper construction details; the second is selecting durable products and materials, the third is achieving durability by reusing existing buildings.

Use construction details that control moisture
Careful design and construction is the top priority in creating a more durable home—and often the most important issue is how we manage moisture. This is a big part of the focus of "building science." The building enclosure (walls, foundation, roof) has to be designed to a) keep moisture out, and b) allow any moisture that does get in to dry out. As we have made our homes tighter and better-insulated over the past several decades, this has become even more important. (The leaky, unheated homes our grandparents built could easily dry out because air readily flowed through the walls.)

Building science is a complex field that is evolving quickly as we learn more about moisture and air movement through buildings and building assemblies—far beyond the scope of this column. But here are some examples that will help to illustrate the concept:

  • Provide deep roof overhangs to keep moisture away from the walls and foundation.
  • Provide good drainage around the foundation, and slope the ground away from the house.
  • Always provide a "drainage plane" or "rain screen" when designing and building walls. This air space between the siding and sheathing allows siding to dry out between rain events and prevents water vapor from being driven into the wall cavity from the exterior.
  • Properly flash around windows and other wall and roof penetrations. Specialized flashing products are available to make this process a lot easier than it used to be.
  • Provide an "air barrier" in the building enclosure that blocks air flow. Experts used to suggest a "vapor barrier," but blocking airflow is more important than stopping vapor diffusion. An air barrier can still be vapor-permeable, allowing moisture to escape over time.
  • Avoid moisture sources in the home (for example, provide quiet bathroom fans that will be used while showering, install an outside-venting range hood fan, and in humid climates insulate even cold water pipes to prevent condensation).

Select durable products and materials
Along with design and construction, the products and materials we install in a home can influence durability. We focus a lot of attention on selecting green building materials (see my #8 priority). When a product has high recycled content, for example, it not only reduces the energy and environmental impacts of extracting the raw materials that would otherwise be required, but it also helps keep material out of the waste stream. In my opinion, though, it's an even higher priority to use very durable materials.

If material A will last three times as long as material B, we have three times as long to amortize the environmental impacts that were involved in producing that material. So even if material A took twice the energy to produce, our selection of that material will have a net benefit over the long term.

Fiber-cement siding, for example, costs a lot more than vinyl siding, but it should last a lot longer. The same goes with high-quality, standing-seam metal roofing or slate shingles, compared with asphalt shingles. There is usually a higher up-front cost for more durable materials, but that extra cost is repaid over the long term—both monetarily and environmentally.

Reuse existing buildings
Part of ensuring durability is renovating older buildings rather than building new. Dramatically reducing the energy consumption of existing buildings makes them relevant to future resource constraints and what are likely to become overriding desires to minimize carbon emissions.

Hire someone with expertise in building science
Very connected to the above two priorities, relative to durability, is to hire someone with expertise in building science. This applies equally to new construction and remodeling. It's complicated—and it's important that your designer and contractor understand what's involved in building (or remodeling) a home in a way that will keep it going strong for hundreds of years.

Summary so far of my top 10 list of green building priorities:

#6. Ensure durability and reuse existing buildings
#7. Protect and restore the site
#8. Use green materials
#9. Create resilient, climate-adapted buildings
#10. Make it easy for homeowners to be green

In addition to this Energy Solutions blog, Alex writes the weekly blog on BuildingGreen.com Alex's Cool Product of the Week, which profiles an interesting new green building product each week. You can sign up to receive notices of these blogs by e-mail—enter your e-mail address in the upper right corner of any blog page.

Alex is founder of BuildingGreen, LLC and executive editor of Environmental Building News. To keep up with his latest articles and musings, you can sign up for his Twitter feed


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  1. Alex Wilson

1.
Oct 13, 2010 5:09 PM ET

a contrasting point of view from your colleague
by Luke

Well done! I agree with everything in this post.
And I'm also finding ways of changing my opinions to understand the 'edge' of improving sustainability in our built environment.
As an alternative point of view that got me thinking about this was Martin's post a year or so ago about "Green Homes don't have to be durable."
http://www.greenbuildingadvisor.com/blogs/dept/musings/green-homes-don-t...

Another way to consider "durability" in a difference sense-- sometimes the hardest durability is the durability of the "program" and service that the home space provides.
I live in a location where there are no longer available greenfields for development. Most projects are in previously developed land. One of the issues that often faces homeowners with whom I engage is the age-old "Remodel vs. new construction" question. Their existing homes are perfectly durable, well detailed, and well detailed and will survive until the next San Andreas earthquake. However, they feel that the space doesn't properly provide all the service they want out of their house. So, they consider remodeling, realize how expensive it is, and then they tear the house down and start anew, as it is currently the cheaper option.
I am not an architect (as my architect colleagues constantly remind me), but the durability of space and program is the one that I have the hardest getting my mind around.
To summarize-- perhaps I work in a self-selecting group of homes, but I always seem to work on houses whose "durability" has failed (and the house consequently torn down) in spite of all the good details and recommendations that you've described above.

I suspect that you'll have some perspectives related to these issues in upcoming recommendations.


2.
Oct 14, 2010 7:28 AM ET

Change and decay in all around I see
by Interested Onlooker

“If material A will last three times as long as material B, we have three times as long to amortize the environmental impacts that were involved in producing that material. So even if material A took twice the energy to produce, our selection of that material will have a net benefit over the long term.” But only if it continues to be used for its original function. If material B can adapt or be re-used and the highly durable material A cannot then the choice is different. Over the timescales which are being considered here buildings, uses and neighborhoods all evolve. The capacity to adapt may become just as valuable as durability. Even if the two slowest shearing layers, site and structure, don’t change greatly the other four (skin, space, services and stuff) certainly will. Designing buildings which allow these changes with minimum disruption and environmental impact is going to be an additional ingredient in the mix of ‘green’ architecture. Real people are going to continue to want to change their buildings as they use them – it is not going to be enough simply to design an ‘optimal’ solution to meet current requirements.


3.
Oct 14, 2010 7:49 AM ET

Durable and adaptable
by AlexWilson

Great comment on the adaptation of buildings and building components over time. This is, indeed, an important issue--and really an aspect of durability. I recommend reading Stewart Brand's book, "How Buildings Learn" for more on this issue.


4.
Oct 21, 2010 1:15 PM ET

Durabilty vs. Decompose
by Charles Brown

Good points by Alex and M Holladay - again reinforcing the argument for integration and thoughtful responsiveness to design program. As Energy & Water appear to be gaining traction as the top two of conservation, I've been asking myself more about topsoil conservation. We do a pretty poor job of conserving soil at present and returning nutrients by decomposition. What LCA I have done tends to favor local inert natural materials like stone and rammed earth, but only because most materials are energy intensive to make and distribute.

After watching a TED talk on the further development of bio-based greensulate http://www.ecovativedesign.com and EBN's article re; the carbon footprint of most board insulation, I conclude we need durability and compostability. To achieve that we'll have to change how we think of building envelope systems. I can't imagine mycelium grown greensulate will have the same moisture resistance as synthetic foam. Current building science is heavily dependent on oil for a combined moisture, air and thermal barrier.

Not saying I have the answer, other than we need to keep imagining many options to achieve a carbon balanced future.


5.
Oct 24, 2010 10:00 AM ET

'How Buildings Learn'
by James Morgan

Important not to be led down the primrose path towards the idea that you can only make durable buildings with so-called 'durable materials', in fact quite the contrary may be true. Mass concrete buildings of the 1920's and 30's were often demolished within a decade or two because of their poor suitability to continued use in a rapidly changing world and the difficulty of physically adapting them to those new conditions. These buildings were impervious to the 'learning' that Brand describes. The durability of a building is the durability of its components not only in a specific assembly in a specific location and climate, but also in a specific cultural and economic context which is subject to changing substantially over time. This is frequently achieved with materials that are inherently quite degradable: the standard American frame house is a prime example. The ability of the structure itself to be easily modified with simple tools and modest skills is important, so is the flexibility of the spaces themselves to adapt to different circumstances without any modification at all. Standard stick framing (with all its substantial redundancies - sorry, smart framers) fits the bill well. So does small-unit masonry construction - brick and block, adobe, straw bale even, anything that can be worked with hand tools and hoisted into place with one or two strong backs and one or two pairs of hands. In my neighborhood cheaply built mill cottages dating from the 1920's (2 x 8 floor joists @ 24" o/c, brick pier foundations on dirt footings) are lasting better, through continued upgrades and in spite of only sporadic TLC, than lift-slab concrete malls. If we want to know how to make long-lasting buildings with low energy loads the lessons are all around us.


6.
Oct 25, 2010 1:39 AM ET

scientific superiority versus long term empericism
by smalld

Present day philosophy concerning modern buildings is nice and highly political if not moneymakers (last 100 years or so) . However why do you never refer to the empirical information obtained over may hundreds or thousands of years in climate very similar if not identical to yours throughout the world. It may simply come down to the ancient Japanese philosophy that it is easy to keep warm but it is also very important to keep cool. Look deep, look long, and look world wide, that is all across the planet and in many places that do not necessarily come to mind. You will find wonder in energy efficiency that has been going on for centuries without your 'scientific approach" but simply by 'empirical experience" over in some instances millenium
Regards
smalld.


7.
Nov 1, 2010 3:47 AM ET

Smart Framing and Durability
by Interested Onlooker

James,
Is there anything in smart framing that makes it inherently unsuitable for the evolutionary development that you describe? The ability of a 'low-energy' house to allow such modifications will depend much more on the simplicity and obviousness of the measures used to keep it watertight and air-tight. The internal, visible and reparable nature of the Air-tight Drywall Approach fits the bill for the latter - perhaps a water-proof wrap (tar paper, felt, Tyvek or its clones, etc.) over sheathing would be most suitable for the former. The wrap would need to be protected by siding, of course, with a rainscreen detail, as required, in wet regions.

The need for future owners to understand how their buildings work will place some limits on how complicated our technical solutions can be. KISS is a fundamental principle if buildings are going to survive and adapt.


8.
Nov 12, 2010 12:24 AM ET

Multi Family vs Single Family
by Janet

I wonder if it is easier to deal with reusing existing multi family buildings vs. houses. At least for the homeowner it certainly would be and in this day and age for low income housing especially, HUD financed projects are often refurbished and reused buildings that are being cleaned up, modernized and very often, made more green. I think when you get right down to it that it is easier to reuse and renovate multi family buildings because the home owner is a development company who understands the benefits financially and the benefits for their reputation by building green. I agree with the comments above and the article, that homeowners simply see starting fresh as cheaper (because it often is) but we need to discuss long term benefits not only to them but to the environment they live in.


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