CNET también está disponible en español.

Ir a español

Don't show this again

Christmas Gift Guide

Insulating shell

Solar thermal

White roof

Air holes

Three-pane windows

Efficient AC units


Castle Square facade

BOSTON--Deep-energy retrofits use a variety of green building techniques to slash energy consumption by as much as 70 percent. The Castle Square low-income housing complex in the South End of Boston is applying those methods in a renovation of the 500-unit complex, making it one of the largest deep-energy retrofits in the U.S., according to developers.

Seen here is the insulation that will be placed on the brick exterior of the building that will seal the building and add an R-40 thermal resistance value. The apartment's tenant organization is looking forward to a new facade which will help it better fit into the neighborhood.

Caption by / Photo by Martin LaMonica/CNET

Here is a graphic depicting how arrays of solar hot water panels will be used on the roof of one of the buildings. The project developers decided to go with solar thermal, rather than solar electric, panels because shading would significantly affect electrical output. Solar hot water panels are also cheaper and generally pay for themselves quicker. In this case, the solar thermal system is projected to cut hot water heating needs by about 35 percent.

Caption by / Photo by Castle Square Tenant Organization

In addition to the thick insulation, the new building will use a reflective white roof, as seen on left. Reflective roofs can significantly lower the cooling load of buildings and save electricity by reflecting heat back into space. Because the building needed a new roof to replace the leaking existing one, a white roof is a very cheap energy efficiency measure. The Department of Energy has a program to put on white roofs during re-roofing projects at DOE buildings.

Caption by / Photo by Martin LaMonica/CNET

Because it's a renovation, there's an opportunity to get access to the interior spaces where air leaks can degrade air quality and leak conditioned air. Seen here is the penetration between the kitchen of one apartment and a downstairs neighbor. Because air flows between the apartments, residents complain about odors and poor indoor air quality. Holes and gaps from pipes or other penetrations will be filled with foam or other air-sealing material.

Caption by / Photo by Martin LaMonica/CNET

One area where the project developers needed to buy more expensive equipment was windows. Instead of leaky sliding windows, these new casement units will be able to close tightly and they have an R-value of 5 compared to 1.3 for the older windows. The window frame is fiberglass, rather than metal, which means that it can't act as a thermal bridge, or conduit for heat loss.

Caption by / Photo by Martin LaMonica/CNET

Through the renovation, units will receive a high-efficiency air conditioner that fits into the window box. Tenants have been buying the cheapest and generally least efficient air conditioners of different sizes. With the new system and the tighter construction, project developers expect that air conditioning load to drop by 50 percent.

Caption by / Photo by Martin LaMonica/CNET

A look at the components to the super-insulation that will be added to the building's exterior. There is a membrane applied to brick, then a layer of mineral wool, and then a foam board with a metal cladding. It will give the building and ceiling an R-value of 40 and seal air leaks.

Caption by / Photo by Building Sciences Group

The Castle Square Apartments, a 1960s-era low-income housing development, will get a makeover on the outside and inside through the green building renovation. It will have a highly insulating exterior with a new look and an improved ventilation system designed to improve indoor air quality. Developers expect that it will get LEED certification from the U.S. Green Building Council. Construction of the project, which is funded by state and federal grants, is expected to cost about the same as a typical renovation and be completed next year.

Caption by / Photo by Martin LaMonica/CNET
Up Next
These were the hottest holiday toys...