Rating System

LEED BD+C: New Construction

Rating System Version

v3 - LEED 2009, v2 - LEED 2.2, v2 - LEED 2.0

Inquiry

Maximum Masonry Construction This CIR is for a proposed Innovation Design credit--Optimal Masonry Construction (OMC)-a design approach developed by the International Masonry Institute (IMI) and the project Architect for the new National Training Center in Bowie, Maryland. This design approach will: 1) enhance the building energy and acoustical performance, 2) minimize the use and cost of construction materials, 3) minimize construction waste, 4) reduce building operation & maintenance costs, 5) enhance the durability and useful life of the building. These benefits are achieved by the following design elements used in the new IMI National Training Center in Bowie, Maryland: 1. Improve building thermal and acoustical performance. Use concrete masonry units (CMUs) for all structural walls-exterior and interior. Their high thermal mass improves indoor temperature control by dampening indoor temperature swings. This also reduces energy costs as the thermal mass acts to store excess heat and "coolth" and then release it to the indoor environment when it is useful. Our DOE-based building energy model does not fully model the effect of thermal mass on building energy use and comfort. So we estimated the effect of thermal mass by increasing the R-value of the masonry components of the walls by 20 to 30% according to industry guidelines.1 The resulting energy savings was about 5% of the total annual heating, ventilation and cooling costs for the two buildings. Using autoclaved aerated concrete results in additional thermal resistance due to the myriad air cells the cured concrete. (We used the same wall system in the Base Case energy model as per the ASHRAE 90.1 guideline for energy modeling-- the energy savings due to masonry construction is "buried" in the prescribed energy savings analysis.) Masonry walls provide superior acoustical isolation that can be further enhanced by filling the CMU cavities with grout or with a poured or foamed thermal insulation. 2. Minimize the use and cost of construction materials. a. Eliminate drywall & acoustical tile. At IMI drywall use was reduced by 97% to lower construction waste, lower project material costs due to fewer wall material components; lower installation costs due to the elimination of cutting, taping, plastering, and sanding steps; lower housekeeping costs, lower Operations and Maintenance (O&M) and life-cycle costs; and reduced likelihood of moisture and/or mold accumulation resulting in higher indoor air quality. This approach eliminates the waste and environmental disturbance caused by the manufacturing of drywall. Not using acoustical tile or any type of ceiling finish also reduces project costs and construction waste. It avoids the cost of maintaining the ceiling finish and improves access to the building infrastructure located at the ceilings; b. Avoid wood and wood-based materials to avoid harvesting old growth forests. Avoid wood-based products and their associated manufacturing processes and binders/adhesives that can adversely affect the indoor and public environment. The IMI project virtually eliminated wood by using steel, stone or concrete lintels and frames. Optimal Masonry Construction makes it more affordable to use small amounts of FSC-certified wood products or drywall with a very high recycled material content.; c. Use high recycled content masonry units (CMUs) that have at least 40% post-industrial recycled content; d. Avoid floor coverings. Over 95% of the floor area will be either durable concrete or terrazzo masonry floors sealed and protected by low or non-VOC coatings. The remainder is synthetic rubber flooring and a small amount of carpeting. For the new IMI National Training Center-the exposed masonry approach avoided an estimated $ 825,000 in construction costs due to eliminating entire building systems. 3. Minimize construction waste. Optimize the masonry system by coordinating the dimensions of the building, the thickness of the wall insulation and the rain screen air gap to minimize/eliminate the number of masonry cuts. This reduces masonry construction waste, construction costs and housekeeping costs. At the new IMI National Training Center this was done by half-overlapping the 8-inch face brick and selecting wall lengths so that there is no need to cut any of the bricks at the exterior corners. 4. Reduce Building Operation & Maintenance costs. This is done by: a. Improved moisture control. The 8-inch brick size and 1/2 overlap pattern used at the new IMI facility leave a four inch space between the outside of the concrete masonry unit (CMU) walls and the inside surface of the face brick. It makes it convenient and affordable to provide a 2-inch wide air gap for good moisture control-considered good practice in the industry.2,3 As described in Part 2a above, eliminating drywall and acoustical tile layers eliminates potential areas for moisture and mold build-up; b. Improved thermal insulation. The 4-inch space also allows for at least a 2-inch layer of continuous rigid board insulation over the CMU wall that greatly enhances the thermal properties of the walls. This is in addition to the added thermal insulation resulting from the high density of masonry walls; c. Decreased maintenance of exterior and interior finishes. As described in Part 2a above, the all-masonry construction and "naked architecture" design approach will reduce the cost of cleaning the building and the cost of periodic refurbishing interior surfaces and finishes. The materials require minimum maintenance except for tuckpointing that is done over 10 year or longer periods. The exposed building systems are easier to access and maintain. 5. Increased building safety, durability and longevity. All--masonry construction ensures the use of materials with high durability and damage resistance that also provide enhanced protection to occupants. Exterior and partition walls of masonry and stone, whether in the form of block, bricks, or poured concrete, are more resistant to damage from natural catastrophes and afford greater protection to the occupants than do drywall and wood products. Masonry and stone walls also afford greater protection to occupants from wind-borne projectiles under tornadic conditions as well as greater fire protection than typical drywall/framed wall systems. Masonry and stone construction make for a durable and long-lasting building. The proposed Innovation Credit would require satisfying at least six of the following design elements: 1) Drywall and acoustical tile cover less than 10% of all interior walls and ceilings 2) Use masonry construction for at least 90% of the structural and partition walls 3) Avoid using wood or wood-based products in the building or furnishings 4) Use aerated concrete for at least 5% of the total wall mass 5) Use a face brick pattern that eliminates avoid brick cuttings at exterior wall corners, 6) Provide at least a 2-inch rain shield space in the exterior walls 7) In climates covering areas such as Bowie, Maryland and further north, install at least 1-inch or continuous rigid insulation outside of at least 66% of the exterior walls mass 8) Use floor coverings are on less than 10% of the conditioned floor area 9) Expose at least 80% of all electrical and HVAC distribution systems. 1. Technical Notes 4A&B - Heat Transmission Coefficients & Energy Code Compliance of Brick Masonry Walls. The Brick Industry. Sept. 1997. 2. Masonry Cavity Walls: Systems and Construction. Section 2.12.4 Technology Brief of the International Masonry Institute. October 2000 3. Technical Notes 27 - Brick Masonry Rain Screen Walls. The Brick Industry. August 1994. p15 Please provide the IMI Project Team with a ruling that will let us know the likelihood of the aforementioned ID Credit Proposal being successful.