Interior and exterior storm windows pros, cons and alternatives

Storm windows can be a cost-effective option for cold climates, compared to common replacement windows.

Storm windows are a lot more inexpensive and can provide significantly more energy savings than cheap replacement windows.

See: Exterior vs. Interior storm windowsStorm windows are a typical cold climate window treatment, intended to increase the R-value/insulation of existing windows.

Sophisticated storm windows – two and three track exterior windows, with low-E glass – will cost you a small fraction of standard replacement windows.

And they may cut heat transfer by 50% or so, which you will never achieve with average windows.

Inexpensive Plastic storm windowsStorm Windows Kits

Many inexpensive storm windows – involving flexible PVC glazing, acrylic glazing and insulation film kits- which a energy- are unreliable and with a short life span.

Plastic interior storm panels will cost you a few dozen dollars and are easy to install and as effective as other more expensive storm windows. But they lose quality overtime (clear plastic will soon lose transparency) or may get broken easily.

Storm windows with Low-E glass and sturdy metal materials at the frames and sashes are a better choice.

Storm windows Alternatives

Windows films designed to reduce heat loss during the heating season are very ineffective when installed applied over the glass.

Only window insulated films (applied to the indoor window frame) are effective at preventing heat loss.

The benefits provided by storm windows, shades, or insulation kits and other window improvements are highest with older and poorly performing windows.

Several manufacturers are offering two and three-cell pleated or cellular shades with dead air spaces. These shades reduce radiant heat loss in cold weather, which is important.

But there is a downside: they only provide slight control of air infiltration.

window comfortThe insulating value of these types of shades depends on their air-sealing value; without an airtight seal around their perimeter, convective currents will short-circuit thermal performance. And since they do not provide that sealing, it’s hard to say their true performance.

Bottom line: pleated and cellular shades should be mounted as close to the glass of the windows as possible; the sides of the shade should held close to the wall in order to get a sealed air space. The reflective surface of the shades should always face inward during the winter.

Adding a second window

Replacing an energy-inefficient window can be disruptive and messy. But if the window doesn't leak and is strong, consider installing a second window on the interior of the existing one. This new window will act as a special and strong storm window andcan be an excellent choice from an energy and an economic standpoint.

Obviously this second window should have the same operation type and a reasonable insulation value.

In cold and moderate climates, if feasible, that's a very effective way of reducing heat loss and infiltration.

Choosing storm windows

Storm windows are a typical cold climate window treatment, intended to increase the R-value/insulation of existing windows with energy-efficiency problems.
They are an alternative to replacement windows, and do not make sense in new construction.
If you are looking for storm windows, prefer units with Low-e glass panes and make sure that the storm window has a sturdy frame (aluminum can provide it), removable sashes (important for cleaning, and a standard feature in new units) and good sealing.

Also prefer exterior storm windows with weep holes on their bottom (to let water out) and without plastic parts.

When installing exterior storm windows do not forget that the primary windows should be properly sealed, to prevent condensation problems (in practice that means that the storm window should be slightly leakier than the main window).

Some storm windows include a screen to keep insects out, whenever the pane is removed for ventilation.

Interior vs Exterior Storm Windows

Exterior storm windows (with a good low-e glass) are significantly more effective than interior storm windows.

Interior storm windowIf you intend to buy an interior storm windows, look carefully at the seals, sashes and frames. Units using magnetic tapes and adhesives do not last long.

Units with plastic glazing will lose transparency over time (due to ultraviolet radiation) and have a short lifespan.

Units with glass (preferable low-e glass, for a better R-value/insulation) and metal parts ensure a longer service life.






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