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Recoup your investment

In a modern home, it's estimated that 25% of all energy loss is through the windows. Which means improving them will show immediate returns. Although exact cost-recovery calculations are difficult since existing windows vary significantly in terms of R-value and air infiltration rates, actual experiences of real customers place the recovery period for interior storm windows offered by D.W. Philpot Company at between 2-1/2 to 4 years.

Save on energy costs year after year

According to the manufacturer, a homeowner in the Boston area would save approximately $440 year on heating and cooling costs using interior storm windows. (Based on calculations done using RESFEN - a window performance tool from Berkeley National Labs in California.)

All calculations are for a 2 story existing frame house with 300 square feet of basic windows, using an electric heat pump with a power cost of 8.5cents per kWh.

A Must for Historic Homes

According to the National Trust for Historic Preservation®, keeping and maintaining your original windows is one of the best ways to preserve the appearance, integrity and character of your historic home. Which make interior storm windows the ideal solution for you. They offer a low cost per window, provide energy savings, are custom-fitted to solve problems like over-sized or odd-shaped openings and they blend in - nearly disappearing on the inside - invisible from the outside.

Weatherization Tips for Older Homes from the National Trust for Historic Preservation

Price Comparison

New name brand window, tilt wash, double-hung, 18" x 36"

Price includes: installation, disposal of old window in landfill and associated costs

Materials needed: interior and exterior casing, possible drywall and paint

New name brand replacement window, 18" x 36"

Price includes: installation, disposal of old window in landfill and associated costs

New second-tier brand replacement window, 18" x 36"

Price includes: installation, disposal of old window in landfill and associated costs

New interior storm window, 18" x 36"

Price includes: installation

Plus, the integrity and character of your home is maintained


Interior storm windows save you money

But you also save on energy costs, save on the amount of time your home is disrupted by installation and save the look, character and feel of your older home.


What do they do?
Interior storm windows provide a layer of additional "insulation" for your windows. It turns single pane windows into double glazed windows or double glazed windows into triple glazed ones. Additionally, they seal air-tightly against the existing window frame and eliminate air infiltration. Measured reductions in sound and heat transfer are often on the order of 60% or more with properly installed windows from D.W. Philpot Company.
How do these windows work?
An interior storm window mounts magnetically to a metal strip that is installed inside your existing window opening. You leave your window inplace, and snap in the window to provide insulation. The dead air trapped in the air gap between the existing window and the interior storm window inhibits heat transfer and controls condensation. It uses a shatter resistant plexiglass pane (a better insulator than glass) mounted in an innovative PVC molding to maximize its insulative value. Since the entire window is made from highly insulative plastic, the window itself provides much greater insulation than aluminum framed windows, or vinyl windows with glass panes.
If acrylic is so good, why aren't my windows made of it already?
Acrylic is much stronger than glass, and it is also a much better insulator. Acrylic is also available with tinting or UV blocking characteristics for museums and medical applications. The reason it is not in widespread use as a glazing material has to do with its heat expansion properties. Acrylic will expand and contract when heated or cooled, enough that it cannot be permanently affixed in a solid frame. The innovative molding design allows us to use it across a wide range of temperatures and manage the acrylic's expansion without bowing or frame breakage.
How do I install them?
We will accurately measure your window opening and order a custom built interior storm window to suit your application. And from a number of different mounting options, we will choose the best one to fit your existing window. We attach a steel mounting angle around the rim of your window opening, and then installing the window is as easy as snapping the magnets into place. The total installation can be done in less than an hour, with no disruption to your living space whatsoever.
What about soundproofing?
The innovative molding design serves to block sound as well as cold. Sound deadening on the order of 60% is typically measured in noisy areas.
How much do they cost?
They are priced according to size. Contact us for more information. The total cost of adding an interior storm window is a fraction of the cost of total window replacement, and you can do it at any time of year with no disruption.
Can I remove them, and open my windows on a nice day?
You can simple snap them out and store them whenever you wish. We also offer a self-storing option for sash windows where you can remove the bottom of a two-piece split storm window and store it magnetically on the top part of the window for a slightly higher price.
How do I get them?
Contact us for more information.
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