New build wanting energy efficiency
Vpachmayer
| Posted in General Questions on
We are planning a new build for next spring. We are wanting to go as Green and energy efficient as possible without breaking the bank.
We are looking into geo- thermal heating and cooling, spray foam insulation, premium housewrap like Enviro-dry.
The home will be built in Northeastern Ohio.
We will have a full walk- out basement (possibly poured concrete or cement block). The houseplans are for 2900 sq foot home with 2×6 framing.
What would you include or cut to save money both during building and long term savings? example: Do you need higher cost spray foam insulation, if using housewrap like Enviro-dry?
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Replies
Vpachmeyer,
Most high performance builders don't use either product. Neither are a necessary part of a new Green build.
V, you've come to the right place for discussions and advice on green building. Looks like you're just dipping your foot into the topic. You'll want to do a few things ASAP: first, keep reading the articles and archives of past Q&A on this site; there is a wealth of knowledge and many of your questions are already answered; second, immediately begin the process of finding a local builder who has some experience with these things. I'm also in Ohio (NW side) and I know how tough that last one is. Wishing you luck as you get going!
To begin the answers to your questions, or at least the dispensing of opinions:
1. Forget geotherm--it's often a complicated boondoggle that can be accomplished with other technology for a fraction of the cost. Air source heat pumps (minisplits) are incredibly capable and efficient these days, even for larger houses.
2. Spray foam is an expensive solution to a very simple problem, and often isn't really a good solution. Plus, it certainly is NOT green. When building new, you have the opportunity to design in more clever and effective insulation, particularly continuous exterior rigid foam or mineral wool. Lots of options--there are many ways to skin this cat.
3. Not sure that premium housewrap is a critical thing. Plain old Typar or Tyvek can be incorporated into an effective envelope. With some strategies (i.e. Zip system, liquid applied weather barrier) you can even design out the housewrap altogether.
4. Try wherever possible to shrink your house and simplify its footprint. By far this is the most effective way to cut costs and increase green-ness.
5. Think through your priorities. Green building inevitably holds your feet (and wallet) to the fire, demanding to know what's really important. Try to take the long view on efficiency, it's what Mother Earth does.
Thanks for the response. We will be building the home ourselves. My Dad will be the General Contractor- so anything we incorporate will be done by our research. That's the part that makes me nervous!
I've been in your shoes. Hire an architect if you want green. They'll save you money. You just said the three things you wanted to be green are not actually green and they're the most expensive options.
Otherwise just be happy with normal construction.
Don't mean to come off as a prude, just that there's a lot to learn in a short amount of time.
I agree. An architect or an energy rater/consultant can make sure that you actually get a efficient, comfortable, durable, green homes. And may save you money along the way. Good call Jamie.
I didn't even know a energy rater/ consultant was a thing. How hard are they to find??
Thanks, energy efficiency is more important to me than green. I guess.
Don't waste money on spray foam. Spray foam is good where it's needed, but it's only needed in a few niche locations: usually cathedral ceiling RETROFITS (new builds can be done differently without it), and certain oddly shaped locations. In a new build, you can often avoid spray foam altogether which will both save money and be more green.
I would use mineral wool in the walls, high-density fiberglass (either of which gets you a bit more R per inch) if you want to save money, and blown cellulose in the attic areas which is about the cheapest and greenest insulation available. I would use exterior rigid foam, at least 2", around the perimeter, and I'd use reclaimed polyiso. I would use exterior rigid foam, probably type II EPS around the basement foundation walls. How you do the walkout part can be tricky depending on exactly how you're building it.
Air source heat pumps are MUCH lower installation cost and still perform well. This is unfortunate since I've always thought geothermal is a really nifty way to do heating and cooling, but it just doesn't make economic sense.
Do NOT confuse expensive products with being most green. A lot of vendors use "greeness" as a way to promote overpriced, or just "more expensive than other suitable options" products. You always need to be watchful for that. Spray foam is an EXCELLENT example of this. You can do an excellent job of air sealing by careful attention to detailing your air barrier, and you can do it with nothing more than a good caulk/sealant (I like polyurethane sealants), and some canned foam (great stuff). After you've done that good job of air sealing, you can use conventional insulation which is both cheaper AND greener. Use the savings for exterior rigid foam which will do much more for the overall thermal performance of your home than spray foam ever would.
Bill
Thanks, I feel like I definitely was getting scammed by the marketing ploys of "greeness" to promote the overpriced products. I will definitely look into all of this.
Hi Vpachmayer.
I agree with the others on the geothermal and spray foam. They are expensive in more ways than one and are unnecessary.
For energy-efficiency and comfort, focus on the building envelope (all six or more sides of the building). The priorities are keeping water out of the building, air sealing, controlling vapor, and insulating. This article explains how that all comes together on walls: The Four Control Layers of a Wall. Slabs and roofs are just variations on the theme.
Here's another article that will give you an overview of the most common approaches to building efficient and durable walls: Walls that Work.
Make a detailed plan for air sealing and test the air sealing with a blower door before closing up the walls so that you can seal any leaks the test reveals. Here are two good articles to read on blower door testing: Blower Door Testing and Blower-Door-Directed Air Sealing.
Once you have your envelope planned, including window and door choices, you can get on to planning mechanical. The good news is that all of the time and money you put into the enclosure will mean that you'll likely need a much smaller mechanical system. We just started a series of articles on mechanicals, including A Beginner’s Guide to HVAC Design and A Beginner’s Guide to Heating Systems. Cooling will be published later this month.
And in a tight house you'll want a Balanced Ventilation Systems to maintain healthy indoor air quality.
Finally, for now, a green house has low embodied carbon. This goal can guide your material choices. You may find this article helpful: https://www.greenbuildingadvisor.com/article/another-look-embodied-carbon.
Please use the Q&A to ask your specific questions and good luck with your project.
wow! thank you. Ill read each of those links.
Let me jump on the no spray foam band wagon and say anytime you see spray foam in a plan it is a big red flag. Spray foam is most often used as a band aid to cover up lazy and or very poor choices.
Be strong and say no to stupid my short list
1 HVAC ducts and equipment in the attic
2 Cathedral ceilings
3 Spray foam
4 Ground source heat pumps (geo thermal)
5 Walls of windows
6 Sky lights
7 Any basement without a drain to daylight.
If this project is about investing in energy improvements that are likely to pay for themselves over time spend about 20 hours of your time to model your home in BEopt. If you enter your bid costs in the program it will identify the choices with the best return on investment.
https://beopt.nrel.gov/home
Walta
I would echo what's already been said, and just offer a summary of key things worth considering:
1. Air Sealing: Who's going to do it? Hopefully, someone who doesn't mind doing detailed, finicky work. Where is your air barrier? Define this for all sides of your home (get this in your construction drawings). Do you want to use air sealing tapes, or liquid membranes?
Ideally, you can make a mock wall assembly that can help you plan out all of your details, including air sealing, insulation, ventilated rainscreen, cladding, and flashings. This will allow you to play around with tapes or liquid membranes, and it'll give you an opportunity to address any potential 'headache' areas prior to the start of construction.
2. Wall Assembly: 2x6 walls with exterior continuous insulation? Or will you consider a double stud wall configuration, or even a larsen truss wall system? A mock wall assembly can help you make a decision in this regard as well.
3. Insulation: What material(s) will you use? What R-values are you shooting for?
4. Roof structure: Trusses or site built? If you can go with trusses, and avoid cathedral ceilings, it does simplify air sealing and insulation details (as Walta hinted at earlier).
5. HVAC: If you get below 1.0 ACH@50 with your air sealing, combined with appropriate levels of insulation, you should be able to use a heat pump system combined with a good ERV for your heating, cooling, and ventilation needs. I would plan for a dehumidifier as well.
6. Foundation: Basement or a slab? Personally, I wouldn't do a crawl space only because it typically ends up being an uncomfortable, largely unusable basement space. Regardless, you'll have to work through the details of insulating and air sealing whatever foundation you come up with.
Finally, just to add to Brian's article suggestions, Building Science Corporation (https://www.buildingscience.com/) was an invaluable resource to us during our design/build.
Also, Hammer and Hand's Best Practices Manual came in handy countless times during our build: https://hammerandhand.com/best-practices/manual/
Another great resource that just recently came online is the website for The Pretty Good House concept: https://www.prettygoodhouse.org/pgh-20
In individual blog posts I link to many online resources (many lead back to excellent GBA articles) that were helpful during the design phase of our own build, which you can find here: https://kimchiandkraut.net/blog/
There's a lot to consider and research (Bill is right to warn you about 'greenwashing'), so make sure you take the time to work through all the details before construction begins. Few things are as stressful as problem solving in the moment while a subcontractor is standing next to you waiting for a final decision. Try to eliminate as many of these moments as humanly possible with good planning (and detailed construction drawings --- they can be your best friend on the job site).
Hopefully these resources can help you save some time as you finalize 'green' details.
During my own build, I regret not asking more questions here on GBA --- it's an invaluable resource, one you shouldn't hesitate to utilize as questions come up during your design/build phases.
Good luck with your research and your project!
Lots of good comments above.
As for cathedral ceilings, if you want them, as we did for our house, you can use raised heel scissor trusses which let you insulate with cheap cellulose and are as easy to air seal as a flat ceiling.