Building an affordable green home
Hello All,
I am very new to Green Building Techniques and best practices but so far I have a general outline of how I’d like to achieve a house I am proud of through following as many green building practices as possible. WE don’t have a ton of extra money to pump into building a green home, but I don’t think building a green home always means spending a lot more money (I could be wrong). In my research it sounds like building on slabs are a great start to following green building practices. We are building in New England where basements are standard and slabs are very uncommon. This is definitely making some of the design phase more challenging, especially when it comes to duckwork. Are my initial outlines for green building practices a good starting point? Are there any flaws you see with the approach laid out below? What would be a cost effective way to run duckwork through the house efficiently when there is no basement? I was thinking we could use opt for floor trusses which we could run the ductwork through, but could this be costly.
1) Building on a slab rather than a basement (No radiant floor heating)
– Save on excavation cost – disturbing less of the environment
– Finish the slab as our flooring – savings on flooring cost and reducing building materials
– Eliminate the materials needed for joists and plywood for first floor
2) Large Passive Solar windows to work in tandem with the thermal mass advantages of the concrete flooring. Minimize heating energy and costs in winter.
3) Insulate the shell well.
Any advice or thoughts would be very appreciated!
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Replies
Hi Matthew.
The term "green" can mean different things to different people. And though the goals of low-embodied carbon, energy-efficiency, durability, healthy indoor air quality, passive suitability, etc. often align nicely in a building project, it may be helpful to put some thought into your priorities. Having an ordered list of what is important to you will help you make decisions when the budget gets in the way.
Many high-performance builders keep costs down by opting to build on slabs and as you are thinking, this becomes even more cost-effective when the slab is used as the finish floor. Some people don't like the look and others feel concrete floors are hard on the body; lots of people love them. Ducts can be run in floor trusses, plenum trusses, insulated attics, etc. Check this out (Keeping Ducts Where they Belong) for more on running ducts in slab-on-grade homes.
Some green builders are turning towards concrete-free slabs to minimize the high environmental impact of Portland Cement. This is what I am referring to: Minimizing Concrete in a Slab-on-Grade Home--and it is possible in both slab-on-grade and basement slab situations.
You can stretch your budget far if your design is cost-effective. For example keeping the house as small as possible and the footprint and roof as simple as possible is a lot more affordable than a house with lots of corners, or bumpouts, dormers, valleys, etc. these details also complicate water management, air-sealing, and insulating details.
Some more random thoughts that may be helpful:
If you are counting on solar gain and thermal mass for heating efficiency, you should hire someone to do energy modeling for you. This will likely be money well-spent as you think about how to spend on insulation, windows, doors, and other envelope details. The more money and effort you put into the envelope, the less you will need to spend on HVAC (A Manual J calculation is important to get HVAC right. Check out: A Beginner’s Guide to HVAC Design). And air sealing should be tested at the right time so that leaks can be identified and sealed through Blower-Door-Directed Air Sealing.
That's what comes to mind at the moment. Please ask as many specific questions as you'd like. There's a lot of combined knowledge here on GBA.
To reduce long term heating/cooling costs, insulation and air sealing are key. Insulation is pretty straight-forward but minimizing air leakage is pretty tough. You probably want to hire a builder who has experience with that.
This is probably stating the obvious but if you're building on a slab in NE and using it as the floor, you'll want to make sure you have sufficient insulation under the slab.
Bravo for reviewing options now in the (pre) design phase when you can save a ton of money and headaches and avoid a lot of costly mistakes. Take your time now and have a complete plan including detail drawings BEFORE you start.
Becoming a GBA member is the first step to saving yourself a lot of money during a new build. Then you can start picking off the articles that are referenced in Martin Holladay's "How to Do Everything" article.
Once you've started collecting your ideas, then you can look for an experienced builder in your area that you feel can work with you to turn your ideas into buildable concepts and details drawings.
Final thought - air sealing is more important than you think. Find a builder that understands air sealing and uses a blower door; this will go a long way toward finding a "green" builder.
Check out these GBA articles:
"Building a Low-Cost Zero-Energy Home"
"Green Building for Beginners"
"Martin’s Pretty Good House Manifesto"
"Ten Ways to Improve a New Home"