High Performance Energy Saving Design for the Karuna House Part 1 – Foundation Design
Hello everyone! I hope your holiday break went well. I had a fun time with my family and definitely felt like I recharged my batteries as well. Hopefully you guys could do the same. Today I want to start a series of blog posts on a detailed overview of the high performance systems used in the Karuna House created by Holst Architecture and Hammer & Hand.
The Karuna House is a house designed to meet Passive House standards, Minergie-P-ECO, and Platinum LEED Home Standards. The client is a leading proponent of high performance design technology for climate control. This house is intended to be a case study in the usage of the current technology on the market today. In the first part of this blog post series, I am going to discuss the design of the foundation and the energy saving technology applied in that part of the design.
The main concern for the foundation involved insulating the basement and foundation. With that in mind, most of the technology focuses on maintaining a good quality building envelope that insulates well. The first step was the cut and fill for the excavation. In this step, the cut was balanced with the fill to ensure that there wasn’t a need to haul around aggregate to complete the fill process. For the next step, an Expanded Polystyrene (EPS) geofoam foundation insulation was placed around the cut and fill earthwork before the concrete foundation was constructed. Next, the footings beneath the structure were placed and a moisture blocking capillery break material was placed on top of that. Once the footings were in place, gravel fill was placed for the foundation base and the basement foundation wall was constructed with a vapor barrier extending to both sides of the wall. The concrete mix used in the basement foundation wall consisted of 30% fly ash and used locally sourced aggregate. In order to obtain better energy efficiency, EPS was placed in critical thermal bridge sections. Along the foundation walls, a product called a drain board was applied to it’s surface as well to allow water to flow down the foundation walls and past the footings. Once all that was completed, they applied the vapor barrier over the gravel base and laid some more EPS foam before they constructed the slab portion of the foundation.
My take away from reading the article and watching the videos is that there are two critical issues that affect house foundations – moisture control and thermal bridging. The designers used the EPS and vapor barriers to address these issues. Along with that, methods of construction were used that reduce the use of energy/material in construction as well. Overall, I think this was a good application of some practical design ideas. A lot of designs like this get caught up in following the latest complex and cool looking trend instead of finding a solid and fundamental solution to the problem – this design avoids that fairly well.
What are your thoughts on the design? Does it seem like a practical application to use for increased energy efficiency? Any issues you worry about over it’s life cycle? Thanks for your time and have a good week! 🙂
Hammer and Hand, “The Karuna House: Foundation System”, http://goo.gl/C9Hccu