[Recent Reader Question]
Subject: Insulations levels in a passive solar house
I’m interested in building a passive solar house using Insulated Concrete Forms (ICF) walls, R-60 ceiling. What’s appropriate for under-slab in total R value?
Now, back to your question, the answers that I may offer will vary, depending on your goals for the project. If the goal of the project is to meet the Passive
House (PH) standard of efficiency, I recommend that you have a qualified
Passive House Consultant enter the project plans into the appropriate
energy-modeling software. This is the only way one can ascertain appropriate R-values for the various components within a project.
The super power of the PH approach is that the designer and the builder will know exactly what each specification needs to be, and why. Cost/benefit
tradeoffs become easy to model, and in the end it can be said with a high
level of confidence how much heat will need to be delivered by the home’s
mechanical system, whether or not the home will overheat in the summer, etc.
There is no prescriptive path that will achieve the PH standard, because
every home represents a differing set of climate conditions, design elements, and site conditions.
Please note there is are very real benefits to hitting the PH standard of
efficiency: the home can be heated with a source that is equivalent to a
hair dryer, and saving money by not installing typical or higher cost
mechanical systems will free up funds that are better spent on the home’s
thermal envelope. In a PH, the energy savings will pay for thermal upgrades
in a just a few years. After the point of breaking even financially, energy
savings will accrue to tens of thousands of dollars over time. Actually, in some homes, the homebuyer can save money up front when ‘going Passive’ vs. other methods of construction. The trick is to work with qualified designers and builders and to perform Passive House Energy Modeling as part of the process.
Published on November 30, 2011.