Roll Shutter Product Data

Insulated window shutters can lessen considerably the amount of heat lost through windows. A standard double-glazed window has a thermal resistance of about R2 (RSI 0.35). An insulated shutter with a resistance 2 to 3 times that of a window, say R5 (RSI 0.88), will reduce substantially the energy loss of that window, particularly at night when the house does not benefit from solar radiation. Many different kinds of window shutters are now available. This Note has been prepared as a guide in selection as there are a number of key points to consider to achieve an effective and relatively trouble-free operation of a window shutter.

In choosing, designing, or building an insulated window shutter, the principal fact to consider is its location with respect to the window. The preferred technical option is to position a window shutter so that it covers the outside of a window and can be operated manually or electrically from the inside and perhaps automatically by a programmed timer. A second option is to design and build a window shutter that will operate within the cavity of a double-glazed window, i.e., between two single panes of glass. A third option, which is the easiest and perhaps least expensive but least desirable, is to attach an insulated shutter in the room side of a window assembly.

Shutter on Room-Side of Window:

With an inside insulated window shutter it is probable that condensation and perhaps icing will accumulate between the glass and the shutter during prolonged cold spells. This occurs as a result of room air seeping in and around the shutter and perhaps by diffusion through the shutter material. To control this, it is necessary that the shutter be air tight to the window and that the shutter’s construction has a high resistance to the flow of moisture from diffusion. Control of diffusion is easily achieved if the shutter composition includes a layer of aluminum foil or a heavy sheet of plastic.

Shutter Between Panes:

This system, which is designed to be operated between two panes of glass, is a more efficient arrangement. When a shutter is inserted between two panes of glass, such as a roll-down curtain or polystyrene beads, the inside light of glass will warm up slightly, thereby reducing any window condensation. When the shutter is opened the window panes will not be subject to thermal shock as both panes are at a temperature close to equilibrium condition, cold on the outside and warm on the inside. There is a drawback to this approach however, particularly if space in the wall or ceiling is required to accommodate this type of shutter. Some of the energy savings may be lost if the thermal resistance of the adjacent wall or ceiling is reduced to improve that of the window. Roll-down systems and the bead wall circumvent this difficulty. If the shutter happens to remain closed for a day, the cavity may heat up to a very high temperature resulting in undesirable glass stresses or detrimental effects to the shutter composition. Cleaning and general maintenance of the window will naturally increase.

Shutter on Window Exterior:

This is perhaps the most desirable option as it eliminates the difficulties previously described. When an outside insulated window shutter is closed, the window glass will warm up to indoor temperatures thereby reducing, if not eliminating altogether, the potential for condensation on the window glass. The air tightness of the shutter system is not critical and the diffusion characteristic is immaterial. When the window shutter is opened for daytime use, the window may experience rapid cooling in its central region. Although this effect induces a compression stress at the edge, the window can easily cope with this as it is opposite to the stress that occurs with an inside shutter system. When the window shutter remains closed all day, the window will not experience any adverse effects. The two main problems in connection with this system are: 1) the accumulation and control of snow and ice and the effect of strong winds on the shutter 2) the design of the control mechanism required to operate the system from the inside. Although this is the most desirable option from a thermal point of view, it may prove to be the most costly.

Types of Window Shutter Systems:

There are a variety of window shutter systems on the market, including:

  1. Rigid insulation types that slide into a wall cavity either horizontally or vertically.
  2. Roll-Down curtains composed of layers of highly reflective material that have air space between the layers.
  3. Rigid systems mounted on hinges which swing out or in
  4. More expensive systems, such as the bead wall utilizing styrene bead insulation which is blown in between glass plates.
An insulated window shutter may be cost effective, particularly if it is operated consistently throughout a heating season. A computer study of a typical 2-Storey house has shown that 150 sq. Ft. ( 14 metres sq.) of shuttered windows closed between 11 p.m. and 7 a.m., having an R-factor of 5, saved 18% of the fuel bill of a house operated in Ottawa and built to the requirements of the National Building Code of Canada (1975 Edition). This is $72.00 of a $400.00 fuel bill. This is an example case only; the heat energy savings to be expected of insulated shutters must be determined for each shutter type, hours of operation, and specific building features..

Warnock Hersey Professional Services Ltd.
3210 American Drive, Mississauga, ONT L4V 1B3 Telex: 06-968801

Report No. 1
March 27, 1985

Description: Test of Rollshutter (Moveable Insulating Device) Project Supplied By Client: Rolco Rollshutters Inc. 101A Fisher Street, Okotoks, AB T0L 1T0 Attention: Mr. Bert Weigel


This report covers the results of tests performed on a sample submitted for Canada Mortgage and Housing Corporation approval. Testing was performed in accordance with the C.M H.C Standard for Moveable Insulating Devices.

Sample Description

An exterior mounted roll shutter device incorporating interlocking slats of roll formed aluminum filled with polyurethane foam insulation. The slats move in tracks secured to the window jambs and are activated by a hand crank assembly. General Construction details are shown in the drawing entitled "Rolco Rollshutter" dated 4/84. A copy of this drawing stamped "Warnock Hersey Professional Services Ltd." is included with this report.

Size: to suit window area of 1050 mm wide by 1800 mm high.

Test Results

Initial Operation

Force required to operated unit: 8 N. The maximum allowable is 88 N.

Cycling Test

After 25 cycles, the nylon bearing locating the fixed side of the universal joint in the housing broke and the shaft separated from the unit. The shaft was repaired and the cycling test continued without the nylon bearing. 1500 cycles were completed without further failure or damage.

After cycling, the force required to operate the unit was 8 N.

Blow Out Resistance

The sample was subjected to a pressure differential of 300 Pa to simulate negative wind loading. No breakage or other damage was noted. The force required to operate the unit remained at 8 N following this test.

Thermal Resistance Test

The portion of the device intended to cover the 1050 x 1800 mm window area was mounted onto a simulated window together with the minimum perimeter framing necessary to support the shutter screen at the sides and to provide a sill at the bottom to achieve closure. Plastic Sheet was dropped over the top of the specimen to simulate the partially open nature of the header box in which the rollshutter is stored. The R-value of this configuration was determined. The operating shutter was then removed, leaving the perimeter framing in place and the R-value over the window area was determined again.

Each R-value is that of the specimen (shutter over simulated window or simulated window alone.), based on the interior and exterior calculated average surface temperatures over the prescribed window area of 1050 x 1800 mm ( 1.89 meter sq.).

The results were as follows:

Rollshutter Absent: Tai = 19.79
Tao = -29.23
R= (Tsi - Tso)A
Tsi = 6.13
Tso = -23.47
Q = 264.90
= .211 meter sq. * c

= 1.20 ft. sq. * F

Rollshutter Present: Tai = 19.99
Tao = -29.90
R= (Tsi - Tso)A
Tsi = 9.92
Tso = -25.86
Q = 185.80
= .364 meter sq. * c
  R-Value Added = .153 meter sq. * c

= .87 ft. sq. * f

Where: Tao = outside air temperature (degrees Celsius)
Tai = inside air temperature (degrees Celsius)
Tso = outside surface temperature (degrees Celsius)
Tsi = inside surface temperature (degrees Celsius)
A = window area = 1.05 m x 1.80 m = 1.89 m. squared
Q = heat flow through window area (watts)

Equilibrium surface temperatures were taken at the ¼, ½ and ¾ window heights on the midline of the interior and exterior surface. The results are presented in the tables below.

Rollshutter Absent Surface Temperatures (degrees Celsius)

Inside Air Temperature: +19.79
Outside Air Temperature: -29.23

  ¾ height 2.9 -24.70  
  ½ height 2.8 -24.50  
  ¼ height 2.3 -23.90  
  Average 2.7 -24.40  
Rollshutter Present Surface Temperatures (degrees Celsius)

Inside Air Temperature: +19.99
Outside Air Temperature: -29.90

  ¾ height 11.70 -26.20  
  ½ height 9.40 -26.50  
  ¼ height 7.60 -26.50  
  Average 9.60 -26.40  

Section 9.2 of the Standard (Effect of Condensation on Interior Devices) was not performed, since in our opinion, the device does not rely on reflective surfaces for an appreciable portion of its thermal resistance.


With the exception of the breakage to the operating mechanism noted, which did not impair completion of the test, the sample unit met the requirements of the Canada Mortgage and Housing Corporation Standard for Moveable Insulating Devices for operation, cycling, blow out resistance and thermal resistance.

Respectfully submitted,

Warnock Hersey Professional Services Ltd.

M. F. Chell, P. Eng.
Physical Testing Services
Vern W. Jones, C.E.T
Physical Testing Laboratory

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