Making the frame
It is preferable to fit insulated shutters on the inside of windows or glazed doors (which must be draught-sealed first) so you don’t have to go outside to close them at night. Also, internal shutters do not have to stand up to the elements and are therefore easier to make.
The first step is to fix a frame round the opening to which you want to fit the shutters. This frame provides something for the shutters to close against and allows them to be hinged. It can be of suitably sized planed softwood; a good thickness would be 26mm (32mm before it is planed). The wood must be thick enough to be quite rigid, so that it will not distort when fixed and cause the shutters to stick.
The frame should be as wide as the shutters are thick plus about 25mm to allow for a stop to be nailed on. If the shutters are to fold back against the wall, the frame should be fixed more or less flush with the surface of the wall; if they are to fold against the sides of the opening, the frame can be fixed against the existing window or door frame. If you are fussy about such things the corners of the new frame can be mitred but it is much easier to make butt joints, and they look quite acceptable.
Pack out the frame members with pieces of plywood, hardboard or scraps of wood if the opening is not square. Now check the vertical pieces with a level to ensure that they are upright, or the shutters will not hang properly.
Check that the frame is square by measuring across both diagonals—the measurements will be equal if the frame is square. If the frame is out of alignment it will be difficult to make the shutters so it is worth taking some time to get all this right. When you are satisfied that it is square, screw the frame into the opening with no 10 or no 12 screws and make sure that it is rigidly fixed.
Making the shutters
Once the frame is in place the shutters can be made. Their thickness will be governed by various factors such as cost, the space available for them to fold up in and the desired insulation value. As an example, a shutter made of 50mm thick expanded polystyrene covered on both sides with 4mm plywood will reduce the heat loss of a double-glazed window from 3.4 Watts/m2degC to 0.5 Watts/m2deg C, while a similarly constructed shutter containing 25mm of insulation used on a single-glazed window would result in a reduction from 5 Watts/m2degC to 0.8 Watts/mm2degC. The practical limit to insulation thickness is about 50mm; otherwise the shutters would become very unwieldy.
The simplest way to make the shutters is to use expanded polystyrene which is fairly cheap and very easy to use; glass fibre, expanded polyurethane, mineral wool and similar materials are all suitable. If a rigid material like expanded polystyrene is used it will improve the stiffness of the shutters. Whatever insulation you choose it will need a facing to protect it from damage, and an edging so that hinges and handles can be fixed to the shutter.
To make the shutters, measure the inside dimensions of the frame that you have fixed into the opening and then decide how many shutters you wish to use to fill the space. The fewer shutters you need the easier they will be to make and fit but the more space they will take up when open. A larger number of narrow shutters will occupy less space when open but will need more skill to make and more hinges.
The facing of the shutters can be 4mm plywood or hardboard. Divide the measured size of the frame opening into equal parts according to the number of shutters required and cut the facings to these sizes.lt is better to make the facings too big than too small as they can always be planed down to fit. The edgings of the shutters can be of 25mm x 25mm softwood if you are using 25mm insulation, or 25mm x 50mm for 50mm insulation. The wood need not be planed.
Cut the two edgings for the long sides of a shutter first, making them the full length of the facing, then glue and pin the facing to the softwood edgings. Take care to use a glue that does not damage your insulating material; PVA glue (such as Evostick Resin W) and the traditional hot melted Scotch glue are both suitable for use with expanded polystyrene. Cut more pieces of edging to fit on the two short sides, plus internal cross pieces at intervals of about 400mm, and glue and pin all these into place. Keep the panel pins well in from the edges of the shutters so that they will not get in the way when the edges are planed. When all the framing has been fixed to one facing, cut pieces of insulation to fit tightly into the spaces between the wooden members, push the insulation into place, spread glue on the frame, and pin the other facing into position. Let the glue dry and the shutter is complete.
This description shows a simple method of construction but all sorts of refinements are possible. For example, the edgings can be rebated so that the edges of the facings do not show, or the facing could be of pine match-boarding to give a better appearance. The only essential is the insulation, as it is this that makes the shutters energy-conserving rather than purely decorative.
Fitting the shutters
Having been made the shutters must be put in place. First, plane them so that they fit snugly into the new frame. Use the longest plane you can get to plane the long edges; if possible use a jointer plane with the blade set to cut very shallow. The longer the plane and the shallower the cut, the less chance there is that you will end up with two concave-edged shutters that do not meet in the middle. This problem is worse for large numbers of shutters because there are more edges to get right. Check the fit of the shutters frequently to avoid planing off too much. For the short ends, use the plane from the sides to the middle to prevent splitting the end grain of the edgings.
It is possible to nail a stop to the frame, fit handles to the shutters and push them into place; when not in use they could be hung on the wall. However, the shutters are easier to use and therefore more likely to be used, if they are hinged to the frame. A single shutter can be hinged at the side, top or bottom, although if top-hinged it will need a catch to hold it up. A pair of shutters or multiple shutters must be hung from the sides. The best fit is obtained by using ordinary butt hinges recessed into the shutter and frame, but flush hinges which are screwed to the face of the work and do not need a chiselled recess can also be used. The gaps between the shutters from using surface-fixed hinges can be filled with a draught strip, or ignored. For shutters that are to fold against a wall parliament hinges may be useful. These allow the shutters to swing out to clear skirting boards, architraves, picture rails and other obstructions.
Once the shutters are hinged in place, nail a strip of softwood as sold for doorstops (finished size 8mm x 19mm is available) to the frame for them to close against. Fix some handles to the shutters so that you can open them. If you find that the shutters do not stay closed you can fit a pair (or possibly more if there are several shutters) of small bolts to hold them shut. The bolts should be screwed to the timber edgings of the shutters, not just to the facings. Finally treat the frame and shutters with a clear finish, a coloured stain such as Sadolins, or ordinary paint as required.
If you want to have conventional curtains with your insulated shutters so that you can, for example, use curtains in the summer rather than shutters, lengthen the curtain rail so that the curtains can be opened enough to allow the shutters to be folded away. If the shutters fold against the sides of the opening and project into the room use extension brackets to mount the curtain track far enough out from the wall for the curtains to clear the open shutters.
Once the shutters are finished you will only have to remember to close them when night falls in order to gain the benefit of the extra insulation.