The single most important thing you can do to reduce your energy consumption and costs is to ensure that you have a tight building envelope -- the building's roof, walls, windows, and doors, in other words the envelope, or separation, that controls the flow of energy between the interior and exterior of the building. Insulation and the building envelope are inseparable components in the analysis of how to control heat loss and heat gain and, consequently, save energy and create a more comfortable living environment. A “tight” building envelope refers to maximizing the integrity of the building envelope to reduce or eliminate heat loss and gain.
Brownstones are particularly prone to leaks and draughts due to the natural settling that would have taken place over the last 100 to 150 years since their construction, causing cracks and gaps to form in the building envelope. Additionally, they are replete with single-pane non-insulated windows that may be just as old, and with exterior walls that may completely lack insulation -- we discovered, for instance, that the rear exterior wall of the parlor floor of 168 Clinton St. was constructed with a 6-inch gap between the interior plaster wall and the brick, with no insulation whatsoever, even though it was apparent that the wall was not original because the lathe was metal and not wood (we know the wall dates back to the 1940s at least).
Frequently, as was the case with the lovely bay windows in our brownstone in Park Slope, there is no insulation in the wood millwork and around the windows which explained why the new replacement windows installed by the prior owner did not eliminate the persistent draughts.
A typical brownstone which has not been insulated and maintains its original single pane windows experiences complete air replacement about 6 to 8 times per hour, compared to a well-built new home which typically boasts 1 to 2 air changes per hour – this means brownstones are heating all new air 6 to 8 times per hour! On the bright side, starting out with such a bad track record makes for very dramatic results when you institute improvements!
Building green does not have to be sexy. Insulation does not have a lot of flashy bells and whistles, but it is one of the most effective things you can do to save energy. The holistic approach, however, also takes into account indoor air quality – a warm house in the winter and a cool house in the summer is still not comfortable if it gives you headaches or otherwise makes you sick, so choose your insulation carefully.
This Article will guide you through:
The Basics of Heat Gain and Loss
The Basics of Insulation
Insulation Materials Options and Planning
Health and Indoor Air Quality Issues and Insulation
Eliminating Leaks - Sealing Cracks and Gaps
The Role of Windows in the Building Envelope
|Type of Insulation||Material||R-Value per inch|
|loose-fill||cellulose||3.1 - 3.7|
|fiberglass||2.25 - 4|
|mineral wool||2.4 - 4.0|
|blankets or bats||fiberglass||3.4 - 3.4|
|mineral wool||3.1 - 3.4|
|high density fiberglass or mineral wool||4.0|
|rigid board||expanded polysturene beadboard||3.5 - 5|
|polypolyisocyannurate (foil faced)||5.4 - 7.5|
|blown-in insulation||cellulose||3.2 - 3.7|
|fiberglass||3.2 - 4.1|
|polyurethane foam (from petrochemicals)||5.4 - 7|
|soy (open cell foam)||3.7|
|soy (closed cell foam)||5|
|small particle, pourable substances**||vermiculite**, perlite and polystyrene beads, foam plastics||4 or more|
|1 Dropped ceiling||7 Door frames|
|2 Recessed light||8 Chimney flashing|
|3 Attic or crawl space entrance||9 Window frames|
|4 Sill plates||10 Electrical outlets and switches|
|5 Water and furnace flues||11 Plumbing and utility access|
|6 All ducts|
|Caulking Compound||Recommended Uses||Cleanup||Shrinkage||Adhesion||Notes|
|Household Silicone||Joints between bath and kitchen fixtures and tile, metal joints such as gutters.||Dry cloth immediately or mineral spirits.||Little or none.||Good to excellent.||Flexible: cured silicone stretches up to 3x its width and compresses to one-half the width.|
|Construction Silicone||Seals disimilar building materilas like wood to stone, metal flashing to brick, and will adhere to painted surfaces.||Dry cloth immediately or mineral spirits.||Little or none||Good to excellent.||Flexible (stretches and compresses).|
|Polyurethane, expandable spray foam||Expands when curing; good for larger cracks indoors or outdoors. Use in nonfriction areas, as rubber becomes dry and powdery over time.||Solvent such as lacquer thinner, if immediate.||None.||Good to excellent.||Expands a lot to fit large, irregular gaps. Flexible. Can be used at varyng temperaturers. Must be painted for exterior use. Manufacturing process produces greenhouse gases.|
|Water-based foam sealant||Around window and door frames in new construction (will not overexpand and bend new windows); smaller cracks.||Water.||None; expands only 25%.||Good to excellent.||Takes 24 hours to cure and must be exposed to air. Cures to soft consistency. Production does not produce greenhouse gases.|
|Butyl rubber||Seals most dissimilar materials (glass, metal, plastic, wood, and concrete.) Seals around windows and flashing, bonds loose shingles.||Mineral spirits.||From 5% to 30%.||Good.||Durable 10 or more years; resilient, not brittle. Can be painted after one week curing. Variable shrinkage; may require two applications. Does not adhere well to painted surfaces. Toxic; follow label precautions.|
|Latex||Seals joints around tub and shower. Fills cracks in tile, plaster, glass, and plastic; fills nail holes.||Water.||From 5% to 10%.||Good to excellent.||Easy to use. Seams can be trimmed or smoothed with moist finger or tool. Water resistant when dry. Can be sanded and painted. Less elastic than above materials. Varied durability, 2–10 years. Will not adhere to metal. Little flexibility once cured. Needs to be painted when used on exteriors.|
|Oil or resin-based||Seals exterior seams and joints on building materials.||Mineral spirits.||From 10% to 20%.||Good.||Readily available. Least expensive of the four types. Rope and tube form available. Oils dry out and become brittle, material may fall out. Low durability, 1–4 years. Poor adhesion to porous surfaces like masonry. Should be painted. Can be toxic (check label). Limited temperature range.|
| Tension seal:
Self-stick plastic (vinyl) folded along length in a V-shape or a springy bronze strip (also copper, aluminum, and stainless steel) shaped to bridge a gap. The shape of the material creates a seal by pressing against the sides of a crack to block drafts.
|Inside the track of a double-hung or sliding window, top and sides of door.||Durable. Invisible when in place. Very effective. Vinyl is fairly easy to install. Look of bronze works well for older homes.||Surfaces must be flat and smooth for vinyl. Can be difficult to install, as corners must be snug. Bronze must be nailed in place (every three inches or so) so as not to bend or wrinkle. Can increase resistance in opening/closing doors or windows. Self-adhesive vinyl available. Some manufacturers include extra strip for door striker plate.|
Plain or reinforced with a flexible metal strip; sold in rolls. Must be stapled, glued, or tacked into place. Seals best if staples are parallel to length of the strip.
|Around a door or window (reinforced felt); fitted into a door jamb so the door presses against it.||Easy to install, inexpensive.||Low durability; least effective preventing airflow. Do not use where exposed to moisture or where there is friction or abrasion. All-wool felt is more durable and more expensive. Very visible.|
| Reinforced foam:
Closed-cell foam attached to wood or metal strips.
|Door or window stops; bottom or top of window sash; bottom of door.||Closed-cell foam an effective sealer; scored well in wind tests. Rigid.||Can be difficult to install; must be sawed, nailed, and painted. Very visible. Manufacturing process produces greenhouse gas emissions.|
Nonporous, closed-cell foam, open-cell foam, or EDPM (Ethylene Propylene Diene Monomer) rubber.
|Top and bottom of window sash; door frames; attic hatches and inoperable windows. Good for blocking corners and irregular cracks.||Extremely easy to install. Works well when compressed. Inexpensive. Can be reinforced with staples.||Durability varies with material used, but not especially high for all; use where little wear is expected; visible.|
| Rolled or reinforced vinyl:
Pliable or rigid strip gasket (attached to wood or metal strips.)
|Door or window stops; top or bottom of window sash; bottom of a door (rigid strip only).||Easy installation. Low to moderate cost. Self-adhesive on pliable vinyl may not adhere to metal; some types of rigid strip gaskets provide slot holes to adjust height, increasing durability. Comes in varying colors to help with visibility.||Visible.|
| Door sweep:
Aluminum or stainless steel with brush of plastic, vinyl, sponge, or felt.
|Bottom of interior side of in-swinging door; bottom of exterior side of exterior-swinging door.||Relatively easy to install; many types are adjustable for uneven threshold. Automatically retracting seeps also available, which reduce drag on carpet and increase durability.||Visible. Can drag on carpet. Automatic sweeps are more expensive and can require a small pause once door is unlatched before retracting.|
Works similarly to refrigerator gaskets.
|Top and sides of doors, double-hung and sliding window channels.||Very effective air sealer.|
| Tubular rubber and vinyl:
Vinyl or sponge rubber tubes with a flange along length to staple or tack into place. Door or window presses against them to form a seal.
|Around a door.||Effective air barrier.||Self-stick versions challenging to install.|
| Reinforced silicone:
Tubular gasket attached to a metal strip that resembles reinforced tubular vinyl
|On a doorjamb or a window stop.||Seals well.||Installation can be tricky. Hacksaw required to cut metal; butting corners pose a challenge.|
| Door shoe:
Aluminum face attachment with vinyl C-shaped insert to protect under the door.
|To seal space beneath door.||On the exterior, product sheds rain. Durable. Can be used with uneven opening. Some door shoes have replaceable vinyl inserts.||Fairly expensive; installation moderately difficult. Door bottom planning possibly required.|
| Bulb threshold:
Vinyl and aluminum
|Door thresholds||Combination threshold and weatherstrip; available in different heights.||Wears from foot traffic; relatively expensive.|
| "Frost-brake" threshold: Aluminum or other metal on exterior, wood on interior, with door-bottom seam and vinyl threshold replacement.
||To seal beneath a door.||The use of different materials means less cold transfer. Effective.||Moderately difficult to install, involves threshold replacement.|
| Fin seal:
Pile weatherstrip with plastic Mylar fin centered in pile.
|For aluminum sliding windows and sliding glass doors.||Very durable.||Can be difficult to install.|
| Interlocking metal channels:
Enables sash to engage one another when closed
|Around door perimeters.||Exceptional weather seal.||Very difficult to install as alignment is critical. To be installed by a professional only.|