"Green building" is a term used to describe various aspects of building construction and performance that each meets different standards. It may encompass a number of different systems incorporated in a building: heating/cooling, water, electricity, ventilation, energy use. It may also include the consideration of the composition of the building itself and its location.
Each of these aspects can be made "greener" or less so, and so calling a whole building "green" becomes tricky: what if the heating system is super efficient, but the building is made of toxic materials with high embodied carbon? There's also the issue of a "healthy" building– for both occupants and the environment– that oftentimes overlaps with green buildings.
A myriad of green building standards attempt to address the vagueness of the term "green" by requiring building projects to meet certain criteria to earn special certifications. Among these are the U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED) Program, ENERGY STAR for Buildings, and the International Living Future Institute's Living Building Challenge.
Many of these standards were highly complex, overly-ambitious, or inapplicable to the TRS. Therefore, we decided to take aspects of these existing standards and formulate our own specifications and design process that was feasible within the scope of our project.
TRS Green Building Design Process
After reviewing existing green building standards as inspiration, we determined our own green building specifications. We decided to primarily focus on greenhouse gas (GHS) emissions and material health.
Greenhouse Gas Emissions
GHG emissions can be split into two categories: GHGs emitted during the production and transportation of the materials used in the building, known as embodied carbon (note: carbon as a proxy for GHGs), and operations carbon, or the GHGs caused by electricity and gas used in the building over its lifetime.
Our goals were to have zero operations emissions and to try to minimize embodied carbon in materials. We acknowledge the vagueness of the second goal to "try" to minimize the embodied carbon of materials. The challenge here is that materials impact a number of other performance specifications of the building. We did our best to accommodate the needs of all specifications.
Material Health
To accommodate considerations of human and environmental health, we decided to only use materials that are Red List free. The Red List, synthesized by the Living Future Institute, is a list of harmful chemicals that are common ingredients in many standard building materials. Recognizing the complexity of choosing materials, we created a hierarchy of priorities and turned them into a decision tree:
We decided that above all we would avoid using materials containing Red List ingredients. Given that the material was Red List free, we then checked that we could afford it, and finally compared it to other affordable, Red List free options, and chose the lowest embodied carbon option. If two or more materials were comparable in embodied carbon, we sometimes made the decision based on additional factors, such sourcing locally or showcasing an innovative material. We used this process to decide on all major components of the building: the insulation, the interior and exterior siding, and the flooring.
Material Considerations
Insulation
Due to our commitment to avoiding Red List materials and the space constraints of the TRS, we decided to use Havelock Blown Wool insulation. Below is a table of materials we initially considered.
Material |
R-value |
Red List free? |
Cost |
Embodied Carbon |
Notes |
Vendor/Sources |
Wool |
R-4.3/in |
Yes |
$0.11/R-1-ft2 |
2.07 kg CO2-eq/ft30.04 kg CO2-eq/R-1-ft2 |
Wool is a by-product of the New Zealand meat industry. Can install by hand. |
havelock wool |
Cellulose |
R-3.125/in |
Yes |
$0.011/R-1-ft2 |
unknown |
Up to 85% recycled newsprint; requires a blowing machine (cost of which isn't included here) |
greenfiber |
Cotton Batts |
R-3.5/in |
Yes |
$0.10/R-1-ft2 |
unknown |
80% post-consumer cotton. Can be applied by hand. |
bondedlogic |
Rockwool |
R-4.14/in |
No |
$.062/R-1-ft2 |
unknown |
Comes in batts-- R-30 is 7.25 in thick. Can be applied by hand. |
comfortbattbuy |
Spray Foam
|
R-7.4/in |
unknown |
$0.17/R-1-ft2 |
Unknown, but based on knowledge of other spray foams is likely relatively high |
Requires a contractor for installation; blowing agent has a GWP of 1 kg CO2-eq (claim this is 99% lower than other spray foams), but unsure for what unit, or the environmental impact of other components |
demileck |
Siding
We chose cedar shingles and pine shiplap for our exterior and interior siding, respectively. Cedar shingles had the lowest embodied carbon with no need for additional finishing due to being naturally insect repellant and rot-resistant. Pine was relatively cheap and locally sourced in New Hampshire, and also does not require additional finishing when used on the interior. Below is a table of materials we initially considered.
Material |
Red List free? |
Cost |
Embodied Carbon |
Notes |
Vendor/Sources |
Cedar Shingles(2nd Clear Grade) |
Yes |
$1.20/sqft |
~0.526 kgCO2eq/m^2 |
Cedar Bevel used as proxy for shingles |
Longboard Lumber |
Cedar Siding |
Yes |
$3.50/sqft |
1.55 kgCO2eq/m^2 |
none |
Longboard Lumber |
Pine 1”x12” |
Yes |
$.95/linear ft |
1.90 kgCO2eq/m^2 |
none |
Brookside Building Supply |
Vinyl 8”x150” |
no |
$0.96/sqft |
~0.38 kg COeq/ft^2 (Mfg only) |
Contains PVCRough estimate using SM |
Home Depot |
Steel/metal |
Yes |
$0.875/sqft |
10 kg CO2eq/m^2 |
Estimate from 26 steel cladding LCA |
Home Depot |
Shou Sugi Ban cedar |
yes |
$3.50/sqft + materials for burning |
1.55 CO2eq/m^2 + emissions from burning |
Traditional Japanese method of preserving wood through burning. Labor-intensive and adds fire risk. |
Longboard Lumber (Cedar) |
Flooring
Besides the Red List, important considerations for flooring included aesthetics, durability, clean-ability, and deconstruction. With this in mind, we looked to natural-based, hard flooring. Multiple companies now have click flooring tiles, which require no adhesives (which often contain VOCs and make disassembly difficult) and are easy to install, so we focused on those. We also looked into wood flooring, but in the end decided that the Forbo Marmoleum tiles would be best for disassembly and clean-ability, as well as durability. Below is a table of materials we initially considered.
Material |
Red List free? |
Cost |
Embodied Carbon |
Notes |
Vendor/Sources |
Forbo Marmoleum Click tiles |
Yes |
$5.17/ft2 |
Carbon negative |
Easy to install and disassemble, all natural ingredients. |
Forbo |
Amorim Wise Cork Inspire 700 click tiles |
No - a tiny bit of formaldehyde is used |
$4.99/ft2 |
Carbon negative |
Very cool company and product– unfortunate that the clickable tile has some formaldehyde in it! Otherwise very sustainable |
Amorim Wise |
Maple |
Yes |
$2.50/board-ft |
Carbon negative |
FSC certified and locally sourced. We will need to stain the wood. If we go with this option, we should use Vermont Natural Coatings's Penetrating Waterproofer Infused with Juniper (local, Red List free, and produced in a carbon-neutral facility). Wood will be labor-intensive to install and require screws or nails, making disassembly more difficult. May be harder to clean, as dirt can get stuck in seams. |
N/A |