Attics, Peaked Roof Spaces, and Top Floors
If it’s properly ventilated, an attic can be easily insulated with spray foam or loose fill. However, some older roofs were designed without ventilation in mind, which can limit insulation options. In general, well-ventilated attics and spaces under high-pitched roofs stay cooler in summer because they keep heat away from the ceiling and insulation of the room below.
“In a retrofit, look carefully at the installation. What will it take to get the insulation into the building?” Hart says. “In an attic, it’s often quite easy to use a loose fill or a pumped foam spray because it’s an open cavity and the installers can move around.”
However, if your building is of vaulted construction and has a peaked roof, your indoor options are more limited, Hart adds.
“You probably can’t use a blowing hole – it would be very difficult. It’s similar to a wall cavity, except you really need to have some ventilation at the top to prevent moisture condensation up against the roof. It’s easily done on new construction. But on an existing building, one thing you can do is install specially designed roof insulation boards.”
These are made of rigid foam insulation attached to oriented strand boards (OSB), which have 0.75-inch spacers built in. This satisfies the ventilation requirements while still improving the peaked roof’s performance. For more roof insulation choices, see “The Roof” on page 50.
Envelopes of many types are easily insulated from the outside, which minimizes occupant disruption, Osborn says.
“For exterior applications, you would generally use some type of rigid insulation so you’re not intruding on the interior space with people inside the building,” Osborn adds. “Most of the time, you’ll do an overclad, where you apply insulation and a cladding to the existing substrate.”
Lido Beach Towers, a historic beachfront development near Long Beach, NY, opted for this approach to minimize disruption to its tenants. The 184-unit structure, which was converted into condominiums in 1984, suffered from decades of neglect and “repairs” that were merely cosmetic in nature, resulting in water penetration, structural issues, increasing energy costs, and declining property values.
Sto Corp’s renovation team added expanded polystyrene from the outside in a 100,000-square-foot exterior insulation finishing system (EIFS), a lightweight, architecturally designed synthetic cladding system that combines foam plastic insulation with thin coatings in one integrated package.
The $13.9 million renovation project, which included $5 million just for the EIFS retrofit and stabilizing the substrate, also fitted the development with new windows, doors, roof, and balconies. Five units responding to an informal energy survey the following year noted a savings of nearly 42,000 kW – about 32.5% less than the previous year.
“If it’s either hot or cold and you can’t ever get the temperature right, it’s usually due to inadequate insulation and HVAC systems,” Osborn confirms. “It’s a tough balance to get these buildings right because so much of the temperature is controlled by the effectiveness of the insulation.”
Carefully consider aesthetic requirements as part of the selection process. Masonry and brick structures have no wall cavity by nature, so any insulation must be added on top of the stone, similar to a basement’s insulation needs. Foam plastic boards are an option, as with the Lido Beach condos, but they’ll cover up the stone or brick – forcing you to bridge the divide between aesthetic appeal and energy efficiency.
“If you want to preserve the appearance of the brick on the outside, then that forces you to go inside,” Hart says. “The real challenge is when you have a solid brick wall and you like the look of the brick on the outside and inside. If aesthetics dominate and no one is willing to sacrifice the appearance of the brick, you’re stuck with uninsulated walls.”
This is a particularly troublesome problem in New England and similar climates where old, poorly insulated factories have been refurbished for use as office buildings, Hart adds.