By letting in light, skylights can transform a room, making a bathroom seem larger, a kitchen warm and cheery, or a bedroom a place to watch the stars. And because of marked improvements in flashing and quality control, skylights can now
be installed without fear of leaks from outside or excessive heat loss from within.

Where you put the skylight is partly aesthetic and partly structural. If it’s a kitchen unit, catch the morning sun by facing it east. If placed in a hallway, even a small unit provides enough light to let you do without electric light during the day. In a bathroom, privacy is the main issue. Avoid skylights in south-facing roofs unless you’re designing for passive solar gain; such skylights can roast you in the summer. Similarly, skylights in west-facing roofs may create too much heat in the South and Southwest United States. Avoid skylights that straddle a ridge because they are difficult to flash and likely to leak.

SELECTING A SKYLIGHT

Consider a number of things when buying a sky­light, not least of which is the manufacturer. Although sizes have become pretty much stan­dard, quality varies greatly—so ask local contrac­tors or lumber suppliers which brands they pre­fer. Here are a few aspects to investigate:

► Do you want ventilating (openable) or fixed (closed) skylights? Skylights that open can vent excess heat. And turn-tilt models pivot so they’re easy to clean.

► Is it energy efficient? Most units come with doubled thermal-pane glass, but units should also have a thermal break to minimize loss by conduction. A metal frame that’s continuous (inside to out) will wick off a lot of indoor heat. A better bet is sealed wood.

► Does it have step-flashing along its sides (desirable for shingle roofing) or strip flash­ing, which must be caulked to keep water out? If the unit is wide (more than 32 in.), does the maker supply a cricket to deflect water around the skylight head?

Does the unit have tempered glass?

That’s an important consideration if a tree limb overhangs your roof. Your building code may require such glass.

If the unit will be installed beyond reach, how easy is it to open and close? Remote – controlled units with motors can be pro­grammed to open at a given temperature, and shut when an electronic sensor detects rain, but such units are more expensive and more temperamental than manually operated ones.

Can you get units with screens, blinds, shades or polarizing tints? Low-Ecoatings selectively admit light while reflecting heat. Note: There are different coating types for cold and hot climates, so ask your supplier which is appropriate for your area.

Wear goggles and gloves when replacing dam­aged glass and dried-out putty (glazing com­pound). Although a glazier’s chisel will easily remove most putty, use paint stripper or an elec­tric putty softener to dislodge the tough stuff. (But do not use chemical stripper and heat at the same time.) Because direct heat can crack glass, cover nearby panes with a piece of hardboard wrapped in protective foil. After removing the old putty, glazier’s points, and damaged glass, sand the frame lightly, using 180-grit sandpaper.

Prepping the frame. Before applying new glaz­ing compound to weathered sashes, brush the exposed wood with a sealant or a half-and-half mixture of alcohol (or turpentine) and linseed oil. This will prevent the dry wood from sucking the oil out of the fresh putty. Let the sash dry for an hour or two. Then spread a thin bed of putty along the lip that receives the glass. This bed of putty will prevent rattling and seal air leaks. The replacement pane should be in. smaller than the width and length of the frame.

Cutting the glass. After scribing the glass with a glass cutter, gently rap the ball end of the cutter along the underside of the cut—up and down its length—until a clear line develops. Then, with the cut directly over a table edge, quickly snap the waste portion free. If the waste piece is too small to grip, use glass pliers. Note: Old glass is imper­fect and often hard to cut because it’s irregular and often doesn’t break cleanly.

As you place the glass in the frame, press around the edges so that the putty will seat evenly beneath the pane. With a putty knife held almost flat against the glass, push in new glazier’s points until they are half-buried. (Never hammer the points in; you may break the glass.) Sink a point every 6 in., or at least one for each side of the glass. Be particularly careful when pushing points into muntins (the wooden strips between panes); if you push a point in too far, you could crack the adjacent pane. Glass in metal-frame windows is usually held in place by metal spring clips, which can be reused.

Once the replacement pane is held fast by glazier’s points, apply putty generously. Scoop
out a palmful of putty and knead it in one hand until it is soft and pliable. Use your thumb to press the putty into the frame, applying moderate pressure. You’ll recover any excess when you trim, so use a lot of putty now to ensure getting a good seal.

To trim off the excess, hold the knife blade at an angle of about 45° to the glass, with a corner of the blade touching the glass and the middle of the blade resting on the frame. Pull the knife evenly toward you, plowing a steady furrow through the putty. Go back and touch up the corners after removing most of the excess. You

shouldn’t be able to see putty from the inside of the window once it has been trimmed.

If the putty doesn’t stick, either you’re holding the knife handle too high or there is dust on the frame or the glass. If the problem is just the drag of the knife blade across the putty, a bit of saliva on the blade will lubricate it. When the putty has cured for a week, overpaint it slightly onto the glass to seal the putty from weather.

ALL window frames must be shimmed securely. Pairs of tapered shims allow you to plumb and level window frames in out-of-square openings; supporting frame jambs and preventing deflection even as you drive screws or nails through them.

Ideally, you should shim each side jamb within 4 in. of its top and bottom corners, and every 16 in. in between—a minimum of three shim points along each jamb.

If the rough sill is level and uniformly supports the windowsill, don’t shim underneath it. Window makers disagree about shimming the head jamb. Some recommend that you shim head jambs at the same intervals as side jambs; others suggest not shimming at all because if the header sags, shims beneath it could deflect the head jamb. To be safe, follow the installation instructions that come with your window.

As explained on p. 94, you can nail through or below shims as long they’re snug.

At each shimming point, use a pair of 10d galvanized finish nails or 3-in. galvanized or stainless-steel trim-head screws to keep the jambs from twisting. Screws are more expensive but allow you to make adjustments easily. If the shims are green or "yard wet," there’s no need to predrill them to avoid splits; otherwise, predrill. You can easily fill and paint dimpled nail heads and countersunk screw heads in the jambs. Or you can remove the inside window stops, nail through the jambs, and replace the stops to hide the nails.

Window Repairs

Old houses often have ailing windows, unopen – able because they’re swollen shut or entombed in paint. Try to repair windows during a sunny stretch, but have a roll of sheet plastic on hand to
tack over the openings in case a storm catches you by surprise. Above all, be patient, use force very sparingly on balky windows, and wear gog­gles and gloves.

FREEING SASHES

The window may just be painted shut. Rap around the perimeter of the sashes with a ham­mer, using a wooden block to prevent marring. Then run a scraper or a putty knife along the sash edges.

If the lower sash still won’t move, remove the inside stop, which is usually screwed on, if you can find the screws under all that paint. If you can’t pry up the stop, use a chisel to cut it out; stops are easy to replace. But try not to damage the jamb. Once the inside stop is out, pull out the lower sash and disconnect the sash cord if it hasn’t already rotted away. Use a narrow scraper to remove paint or debris from the sash channel. With a putty knife, clean up the sash channels, and then lightly sand them. Try the sash to see if it now slides more smoothly. If so, wax the chan-

Double-Hung Window Elements

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Retrofitting cap flashing takes dexterity. Cut back the siding nails 2 in. to 4 in. above the opening, and pry up the siding so you can slide the top flange of the Z-bar cap flashing under the building paper and siding, while simultaneously holding up the window unit. You can nail the top flange of the Z-bar through the siding, but that’s not impera­tive. Wedged into place, the cap flashing won’t go anywhere.

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nels (a piece of candle works fine) and the sides of the sash, replace the sash, and reattach the inside stop.

If a sash weight has come loose from its cord or chain, reattach it while the sash is out. Access to these weights varies, but there is often a removable panel toward the bottom of each jamb. If there is no such panel, pry the jamb trim off.