Weatherstripping limits air flow around the edges of the sashes and is often installed to improved the energy performance of the window.
When creating an energy-efficient home through air sealing techniques, it's very important to consider ventilation. Unless properly ventilated, an airtight home can seal in indoor air pollutants. Ventilation also helps control moisture—another important consideration for a healthy, energy-efficient home with low maintenance and repair costs.
Your home needs ventilation—the exchange of indoor air with outdoor air—to reduce indoor pollutants, moisture, and odors. Contaminants such as formaldehyde, volatile organic compounds, and radon can accumulate in poorly ventilated homes, causing health problems. Excess moisture in a home can generate high humidity levels. High humidity levels can lead to mold growth and structural damage to your home.
The design of traditional double-hung wood windows is highly effective because it has been developed over the past four centuries. One of the aspects of this effective design is air infiltration. A little bit of air is always moving over the edges of the sashes, keeping the wood dry and decay free. Sealing up the edges of the sashes too much limits this drying effect and can lead to rotten sash and frame joints. Some of the window repairs I have done over the past thirty years were needed because they were sealed up too tightly during the 1970s "energy crunch." Can we learn from this lesson and not seal up our remaining original wooden windows with too much weatherstripping? With that said, weatherstripping does SOMETIMES make good sense.
Different types of weatherstripping are used depending on how the edge of the sash meets or moves in relation to other parts of the window:
Sliding, along the sash edge. as with double-hung windows where the vertical stile of the sash slides up and down in the track along the jamb of the frame.
Sliding, across the sash edge. as with double-hung windows where the horizontal top rail of the lower sash and bottom rail of the upper sash meet in the middle of the window; and as in casement windows where the top, bottom and latch-edge meet the frame.
Compression, pressing the sash edge. as with double-hung windows where the bottom rail of the lower sash meets the sill and the top rail of the upper sash meets the header of the frame; and as in casement windows where the hinge edge meets the frame.
Metal, durable, long-lasting
Silicone Rubber, flexible in cold temperatures, somewhat durable, with a slippery surface.
Santoprene Rubber, which is a combination of EPDM rubber particles encapsulated in a polypropylene matrix. Not as flexible as silicone rubber, but durable enough to last for decades. Surface is somewhat "grippy" and not slippery like silicone.
Plastic, some types such as vinyl are not very durable, and generate pollution and health problems for people where it is produced. Polypropylene plastic and Mylar may be longer lasting.
Traditional Materials: Felt, leather, heavy canvas, cotton and sisal caulking, have been used in the past for weatherstripping. It can be interesting to recreate these when remnants are encountered, though this custom work can be labor intensive. These materials are now considered more "sustainable" and may begin to play a roll in some products and projects.
(see this message in this discussion:
http://historichomeworks.com/forum/view ... 1441#11441)
Pemko product data: http://tinyurl.com/yc527ye
Pemko supplier: http://www.thehardwarehut.com/catalog-p ... ref=259998
Kilian Hardware: http://www.kilianhardware.com/sprinbronwea.html
Randy-Surley Mfg: http://www.randysurleymfg.com/stripping.htm
Installing rolled spring bronze:
Video courtesy of Dave Bowers at http://www.oldewindowrestorer.com
Determine the width of spring bronze needed:
I size and place mine so the edge of the strip touches the edge of the sash in the middle of the surface between the cord plough and the arris. Usually that's the next size down from the thickness of the sash, then I space the strip over from the stop or parting bead to get the edge of the strip right in the middle of the surface.
To fasten spring bronze (both rolled and V) to sash tracks you can use the little bronze nails that come with the weather stripping. The little nails take quite a bit of time to set just right without denting or buckling the weatherstripping. A trim nail punch can help hold the nail then you tap it in with a hammer:
Malco TNP2R Trim Nail Punch
Supplier: Tools Plus http://tinyurl.com/cvdgsxt
Installing spring bronze weatherstrip:
Allign the strip in the sash track making it parallel with the parting bead or stop of the sash track. Set the nailing edge of the strip so the leaf edge will touch the edge of the sash in the middle of the surface between the cord plough and the arris. Sometimes it will be set just touching the stop or parting bead, and sometimes it will need to be spaced over a bit from the stop or parting bead to get the edge of the strip right in the middle of the surface on the edge of the sash that is between the cord phough and the arris.
Loosely tack the bottom of the strip in place with a temporary nail. Then begin nailing at the top, with the nails evenly space at 2" or 3" apart. Begin driving the nails at a slight angle away from the top and straighten the nail as you drive it it. This helps to slightly stretch the strip preventing buckling up between the nails. As you nail check the allignment of the strip to assure it is parallel with the stop or parting bead at the side of the track. When you get within 6" of the bottom, remove the temporary nail and finish nailing the strip.
, straight strips:
- kilianVprofile.gif (41.19 KiB) Viewed 14835 times
Kilian Hardware: http://kilianhardware.com/vshapsprinbr3.html
Randy-Surley Mfg: http://www.randysurleymfg.com/stripping.htm
At the Video Conference replays you can see V-bronze weatherstripping being applied to the edge of the sash:
http://flash.kmi.open.ac.uk:8080/fm/mem ... 0:46:30.33
ridged strip of metal backing with a rib, or tongue, that is fastened to the sash track, the rib fits into a groove in the edge of the sash.
(video by Martin Muller, http://www.doublehungwindowrestoration.com/
Dorbin Metal Strip Manufacturing Company Inc, Kris Duda, located at 2404 S Cicero Ave Cicero, IL. Phone: 708-656-2333, 708 656-9496, email: email@example.com
(they do not seem to have a website, their prices may be significantly lower than Accurate. Call and Kris will email you a catalog.)
Available online at ABSupply:
http://absupply.net/weatherstripping-do ... ndows.aspx
One of the prominent long-time manufacturers was
Accurate Metal Weatherstrip Co.
(Accurate is no longer in business.)
slightly flexible polypropylene plastic backing with a barb that fits into a kerf in the sash, and a plastic Mylar fin centered in a soft fuzzy pile, the pile holds the fin in place, the fin seals out the air
Conservation Technology http://www.conservationtechnology.com/b ... nents.html
All Window Parts http://www.allglassparts.com/product/404507/400204/
Advanced Repair Technology http://www.advancedrepair.com/weather_s ... lation.htm
A single touch of paint on fin & pile will ruin it. Complete all painting before installation. This may happen during future maintenance. With all weathering stripping that has a fuzzy pile, I put a permanent sticker in the sash track that says and shows: do not get paint on the fuzzy pile.
Many types of weatherstripping require grooves along the edges of the sashes. Cutting grooves is easily done with a hand-held router. the Bosch PR20EVSK Colt Palm Grip 5.6 Amp 1-Horsepower Fixed-Base Variable-Speed Router with Edge Guide works well.
At the Video Conference replays you can see Fin & Pile weatherstripping being applied to the edge of the sash:
http://flash.kmi.open.ac.uk:8080/fm/mem ... 0:28:47.89
When a kerf (or groove) must be cut along the edge of the sash, weakening of the sash should always be considered. The kerf is typically 1/16 to 1/8" wide by 3/16 deep. If the sash does not have a cord groove in the edge there is usually plenty of room for the kerf. Also consider if the kerf will weaken the joints significantly. If the sash has a cord groove and is thinner than 1 1/2" there may not be enough room for the kerf between the groove and the face of the sash. Usually there is enough room for the kerf on sash thicker than 1 1/2", although exceptionally wide cord grooves may not leave enough room for the kerf. Sometimes I have filled wide cord grooves with a dutchman and re-cut narrower cord grooves to make room for the kerf. I have also put fin & pile on stops and parting beads.
Stapling Instead of Nailing
If you are doing more than a few windows and your time is worth money a stapler will speed up production.
I use my Arrow T-50 staple gun with 9/16" or 5/8" stainless steel staples to fasten the weatherstripping to the edge of the sash. Here is a replay of the video conference showing how:
http://fm.kmi.open.ac.uk/fm/fmm.php?pwd ... 30.33&fb=0
Window specialists Dave Clark in California and Andy Roeper in New Hampshire use the Duo-Fast EWC-5018 Electric Stapler.
I used to recommend the EIC-3118 stapler, but found that the thicker staples with the EWC-5018 are better at penetrating thicker metal weatherstriping. It is unique from other staplers in that the tip, where the staple comes out, is extended 5/8" so you can get into limited spaces, like the sash track.
Cost: about $220.(plus shipping, plus staples) available online at DHC:
http://www.dhcsupplies.com/duofast_ewc- ... OFsg2fQrqx
Dave says, "I use Duo-Fast galvanized staples. I found even in this mild humid climate the standard staple rust away, especially on the coast. I have not found the galvanized staples to fail me."
Staples: Galvanized, about $10. for 5,000 count box. Stainless staples are nearly 10 times the cost, and are corrosion resistant but may be too soft to penetrate thicker metal weatherstrips. Use "chisel point" staples, not "divergent point."
http://www.amconservationgroup.com/ande ... seals.html
"I am now sometimes recommending against highly effective weatherstripping for two reasons. 1. The human body needs fresh air for good health. In the 1970s the death rate from emphysema went up 500%+. What else happened in the 1970s? We hand three 'energy crunches' and started sealing up our buildings. Health experts say that rise in emphysema deaths rates is directly attributable to significant decreases of indoor air quality. 2. The original intent of the double-hung design is to have some air infiltration which keeps the wood dry and decay free. I have seen too many fine old windows rot out from the "seal it up real good" treatment applied in the 1970s.
There are many many other much more effective ways to deal with energy costs and occupant comfort than installing weatherstripping! Air infiltration at all points in the walls including windows can be significantly limited in this type of building with the installation of dense-pack cellulose insulation in the building's horizontal planes (between floors and ceilings), which dampens the 'stack effect' of rising warm air that sucks in air low in the building and pushes it out high in the building.
Why does "no weatherstripping" sound so upside down crazy? Because everyone has been brainwashed by the consumer economy masters and the building products industry. Can we please apply rational thought and our own experience to weatherstripping instead of trusting the corporations and big government whose only interest is grabbing our money?" -- John Leeke, Portland, Maine
Seal up the Interior or the Exterior?
Whether or not the interior or exterior of the window system (storm or shutters, primary sash, interior air panel, interior roller shade, drapes, etc.) should be sealed up depends on the general climate at the building location. Way up north the interior primary sash or air panel should usually be sealed up during the winter, so warm moist air does not get into the system and condense due to the cold exterior air. Way down south the exterior storm should usually be sealed up during the summer, so the warm moist exterior air does not get into the system and condense due to the cooler air-conditioned living space. Sometimes it depends on the micro-climate along a wall (sunny warm south & west, shady cool north & east) or even at a specific window, or what is happening within that building even within a specific room.
According to information newly released at the recent energy conference in Boston, the DoE is now sometimes recommending NOT sealing up the exterior OR the interior in the in-between states with a moderate climate.
As usual, there are no pat answers, and no "one size fits all" in the real world of caring for older buildings. Everything is a balancing act that requires rational thought and spiritual intuition. Steve has it about right: "...just going by the traditional wood storms I have seen and am familiar with..." Forget what other people tell you and pay attention to the real world around you and the people you serve.
In fact, most of what we do to the windows now has a minor effect when compared to how the building occupants of today use the windows and what the occupants of tomorrow will need (what happens when we run low on energy in ten years and can't air-condition our buildings? There will be a lot of unsealing going on, and a lot of cursing for the sealing up we have done.)
--John Leeke, Portland, Maine
More to come....
Other good weatherstripping discussions:
http://historichomeworks.com/forum/view ... =7108#7108