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Monday, December 16, 2013

Insulating Solid Masonry Walls


Insulate Masonry Walls: a case study of a carriage house

I live in a part of the country where there are a lot of brick buildings. There are many reasons including durability and feel of permanence of the material that brick was so widely used in east coast cities. The main reason, I think, is 19th Century fire codes that mandated in cities to prevent the spread of fire.  When working on an historic structure there are many things to consider. This post will focus on insulating the walls.

Determining actual construction of wall type can be difficult. We had a project in the office, that is the focus of this case study, that was constructed during a time of transition; from solid construction to an early version of the cavity wall. It turned out to be solid, but some investigation had to be done, both on site and at the local historic society, to confirm this. The next is to evaluate the current building code and energy code requirements the design requirements.

Let’s focus on how on updating the insulation of a solid masonry wall. Researching a topic is a good opportunity to test design questions by looking for evidence based information, both the latest and past, to understand if a solution will have its intended affect.  For example, what is the best way to insulate a solid brick wall?  With a wall there are two sides and thus, two location choices: one is to insulate the exterior or insulate on the interior? Which side is best?  What’s the best thickness for the insulation to be? Does the building’s location or history affect this decision? Of the choices I need to make for code, what are the most cost effective ones? In an effort to save energy adding more is usually the direction to go in, are there unintended consequences of doing so?

Often searches don’t initially help you locate the complete or conflicting answers. Sometimes are lucky but often times you have to sift through a variety of sites- some offering good and bad information.  I searched Building Science Corp.com and found an interesting article titled BSD-114: Interior Insulation of Load Bearing Masonry Walls in Cold Climates,( http://www.buildingscience.com/documents/digests/bsd-114-interior-insulation-retrofits-of-load-bearing-masonry-walls-in-cold-climates ) By John Straube and Chris Schumacher; Created 2007.03/22. This article informs you of the dynamics of the solid brick wall and the control of a walls water balance. The article incorporates research from Canada about what was discovered in retrofitted mill buildings where the water balance equation was thrown out of balance by the selected insulation depth. The recommendation, after further analysis and testing that when it comes to insulation less is more and airtightness is a better energy savings strategy for the long term of the masonry wall. It was found that the more insulation you add to the interior of the wall you push the freeze point of the brick wall into the walls interior which it was found caused the wall to spall- or water freezes and causes the brick to become powder.  This information was helpful when going to the code official to explain why we would not be maximizing the insulation thickness. It also please one of the clients who is a preservationist.

Parallel to this I searched another website http://www.greenspec.co.uk/  that corroborated my initial finding and offered another perspective.  Here is their take on the same subject: http://www.greenspec.co.uk/internal-insulation.php.   

We applied the research was a Victorian carriage house (1864-65) that incorporated a French Mansard roof with a selection of classical details including corbelling at the eaves and decorated flat arches at the entry points. The building had a short life as a stable, for the adjacent big house, and a long life as a two horizontally arranged apartments. Over time use and age took its toll on the building.  Our clients directed us to conduct a complete restoration of the exterior elements – this allowed us to restore deteriorated elements and make sure the wall was air and as water tight as possible. The interior was completely gutted and two new modern side by side apartments with a bonus loft space.

Our strategy was based on research and discussions with the mason. We calculated where the dew point would fall on the brick wall. It , not surprisingly, ended up where the articles suggested. As we pieced the pieces of the puzzle together, we looked to our building sections and outlined our strategy. The goal was to implement airtightness and insulation to achieve the best thermal conditions for the interior spaces. We began with a repointing to both sides of the brick wall. For the roof we re-shingled and devised a proper flashing plan for the edges. On the interior we closed cell foamed the entire roof cavity, walls and first floor to separate the basement from the apartments. Here the research on walls paid off by allowing us to correctly insulate with 1-1/2” closed cell foam to isolate interior moisture from brick wall, we applied a drainage plane against the wall and applied wood blocking for the gypsum board on top. The structure was applied to internal ledgers and is attached to the inside face of the wall, not fixed in the actual brick wall. Ventilation of the interior is accommodated with timed flushes by the bathroom fans- this was possible because of the small apartment size.  The insulation package described works in conjunction with an open plan, interior transparency of materials, natural light and passive heating and cooling strategies to create a modern series of living spaces. The articles aforementioned helped us thru building science to have update energy efficiency and preserve the long term help of the buildings masonry walls.

 

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This is a sketchbook of ideas, books, technical comments, projects that are in the office of adaptdesign.  Please feel free to comment and engage with us on the post we enter.