Board-Formed Concrete and Wood Frame Hybrid Structure
Lulu Wu| Posted inEnergy Efficiency and Durabilityon
We are in the design process of building a Barn structure house in CZ4. Our architect suggested using Board Formed Concrete as the construction material for the bottom half of the house and wood frame for the upper half. Our primary concerns are: can the building be made as airtight using the mix of materials and is concrete a good idea at all?
We have no experience in building a home. Subscribing to this forum has been tremendously educational and helpful in making design decisions to achieve energy efficiency and be more environmentally responsible. We appreciate any input and advice. Thank you!
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Replies
Lulu,
A concrete first floor is built a lot like a concrete basement (minus the waterproofing - and you could say minus any purpose). The only reason to use it is aesthetic. It complicates openings, takes up space, and offers little benefit I can think of beyond it may help the building look more like a traditional barn.
Malcolm, thank you so much for your reply. We do like the aesthetic, but definitely not at the expense of the benefits and functionality of a building enclosure.
Concrete is the least green building material. The carbon footprint is enormous.
Conventional construction exists because it is practical. Especially on your first house you're better off doing what everyone else in your area is doing, it's really hard to get contractors who are willing to work outside of their comfort zone. Rather than going with a radical construction, I'd go with a standard construction and then put resources into details -- building envelope and interior finishes -- that make the house nicer.
To DCContrarian,
I'm so grateful for your comment. What you said is completely aligned with my gut instinct. We are new to the area, and we don't have anyone to go to for advice outside of our architect. I can't tell you how relieved I am to have found this forum.
We are basically doing our own research for greener solutions to this whole project and bringing them to our architect and builder. For instance, we are now looking at "The Smart Enclosure" system by 475 High Performance Building Supply:https://foursevenfive.com/3-tiers-of-the-smart-enclosure/.
Have you or anyone had any experience with this product?
Thank you again!
Look into Pretty Good Houses:https://www.prettygoodhouse.org/
While the website is kind of daunting I hope you can get the idea. They're all about practicality. You don't need an exotic structure to build an energy efficient house. Ideally all of the materials and techniques you use should be familiar to your architect and builder, just used differently.
I hate to say this, but if you have to educate your architect on green building you may have the wrong architect. It's not something that can be added on at the end like a hot tub. It has to be part of the whole design and construction process. That's kind of the point of the Pretty Good House.
Thank you DCContrarian for the link. Really good information!
I suspect you may be right. We will be mindful of that and continue to evaluate the best way forward.
To DCContrarian,
I have taken the core points from PGH and "Green Building for Beginners" by Martin Holladay to our architects. The best way to describe their reaction is "lackluster", most likely due to their inexperience and lack of knowledge in this field. Needless to say, we are very concerned. We really need someone who can guide us with the holistic "house as a system" approach and attitude.
我读过你的文章在这个论坛上和波形的来r the impression that you are a building professional engaging in projects in the DC area (although I'm not certain precisely in what capacity). I hope this is not against the rule of GBA to ask if you would be interested in taking on our project as our PGH consultant. We're building a main house and a guest house on a 12.7-acre lot in Aldie, VA. It's important to us to be as environmentally responsible as possible. However, we find ourselves devoid of proper guidance to accomplish that at the moment.
Thank you,
Lulu
Thanks Lulu. I can't take on any new projects right now. I worked all day today (Saturday) and I'll probably work all day tomorrow (Sunday). Then the week begins on Monday.
Thank you for taking the time to reply. Do you have anyone in mind to refer us? It would mainly be on consultation basis, so remote conference via Zoom can possibly work, too. We don't mind that our architects and builder learn on the job as long as they are willing to learn. We hope (maybe too naively) that by injecting a PGH expert into the team, it would energize and inspire the project. Perhaps they will take the PGH concept with them to their next projects and help propel the movement.
Board Formed Concrete can be a very nice but subtle detail. I found it very nice in 5000 square foot cafeteria of a large corporation. As an exterior finish I am not sure how many guests will get close enough to notice such a fine detail. If it would be the interior finish it could be very nice but a little rustic for my taste a home.
From energy point of view it seems like you would want an R25 wall or so, concrete will need foam to get there.
Mixing the material I don’t see as a problem almost every house has a concrete foundation and a wood frame at some point the two meet if that point is a few inch above grade or 15 feet seems irrelevant.
A poured concreted wall is about as air tight as you can get.
It seems to me all the popular choices for exterior cladding are cement or petroleum based. The way I see it a concrete wall has such a long life span that it is a good carbon investment compared to the relatively temporary alterative.
I hope your plan is to die in the barn as an expensive custom barn home seems unlikely to be a good investment over the next 6 years. What I am getting at is if this is not your forever home build something that is more common that is more likely to be an easy sale.
Walta
Thank you, Walter, for your comment.
We do plan to die in the barn :). However, life is unpredictable and impermanent. So, we also have resale values in mind. In addition, there is the question of whether the concrete aesthetic fits well into the surrounding as the project is in a more rural setting. All in all, our focus is to allocate resources in the order of functionality, environmental responsibility, then aesthetic. Your points have added more clarification for us and put more weight on the side of not going with BFC based on our priorities.
Thank you again!
Lulu