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What are inner windows

InnerWindows are custom made, interior windows made to fit each existing window individually.  They are installed in front of the existing glass windows, creating a sophisticated air seal keeping noise and cold and hot air outside the building. Using a computer assisted Pro-Liner system, our highly trained staff creates a computer model of each unique window.

Inner window schematics

Inner window schematics

Odd sizes and distorted window frames are easily accommodated.   High quality ¼ inch acrylic is then hand cut to each window’s unique dimensions.  We use acrylic instead of glass because of its strength, light weight and superior insulating qualities.

Next, the acrylic is fit into a custom built vinyl extrusion track system from Climate Seal.  The track includes a proprietary bellow system which creates a tight seal to the window frame by utilizing flexible bellows and commercial magnet strips.  The bellows expand and contract as temperatures change, maintaining the weather seal and eliminating infiltration. 

Capitol Inner Window frames and bellows

The framing system is made of exterior grade vinyl designed to withstand harsh U/V light without becoming brittle or discolored.  The interior facing portion of the InnerWindow can be custom matched to any color.  For oversized windows, InnerWindows are designed in smaller, partitioned segments to allow for easier maneuverability. 

Capitol inner Window partition windows

InnerWindows are virtually invisible from both inside and outside the building yet provide state of the art insulation by improving thermal performance and virtually eliminating air infiltration.  InnerWindows are easily removed for window cleaning and temperate weather window access. 

Installing inner windows

InnerWindows abate exterior sound by up to 60% and UV light infiltration by up to 85%. If sound or UV light is a particular issue, we offer two enhancement upgrades, the Acoustic Upgrade and the SunGuard Upgrade, to better address excessive noise and to provide additional UV protection.   Acoustic InnerWindows achieve up to an 80% sound reduction with an STC rating as high as 49.  This is accomplished through our utilization of heavier weight acrylic combined with high performance, closed cell acoustical foam.

Click for Sound and Acrylic Data

sound reduction chart

SunGuard InnerWindows provide additional protection against the sun’s harmful UV rays.  This is especially useful in museum applications.  To achieve additional UV protection, we apply a clean and invisible finish to our high quality acrylic material to block 98% of the sun’s UV rays. 

Click for Acrylic Data

How Do InnerWindows Save Energy?

InnerWindows work with the existing windows to improve energy performance and decrease air infiltration.  When added to single pane glass windows, InnerWindows lower the U Factor of the windows  by ___ points and decrease air infiltration by 16%.  That translates into reduced energy bills and significantly improved comfort.

InnerWindows=__% Lower U Factor

InnerWindows lower the U Factor, or thermal heat gain, of the windows.  The lower the U Factor number, the greater the insulating value of the window system. U Factor is relevant in both the cold and hot weather. If you touch your existing glass windows on a cold day, the glass will feel cold.  You are paying to continuously to heat that glass surface while it is being bombarded with cold air from the other side.  An InnerWindow installed with that existing glass window will feel much warmer.  Quite simply, the InnerWindow has created an insulating air pocket between itself and the glass window.  The air pocket keeps the interior surface warm, blocking the cold air and dramatically eliminating the transfer of heat to the outside.  On hot summer days, InnerWindows keep your interior windows cool in much the same way.

u factor coparison chart

Click for U Factor Lab Test Data

As the above chart demonstrates, adding InnerWindows to any single pane glass window dramatically lowers the U Factor of the window and saves between $14.80 and $22.20 per window per year.  In fact, adding InnerWindows results in a lower U Factor than replacing the window entirely.

Inserting an Inner Window behind your existing exiting windows results in U-Factors (insulation values) that are BETTER than new replacement Vinyl windows.  This allows you to keep your existing windows, improve the comfort of your home AND, keep some money in your wallet.

In addition, InnerWindows protect your windows from condensation.  In some buildings, the warm, moist interior air creates damaging condensation when it contacts the cold window glass, destroying window frames and walls.  InnerWindows eliminates condensation by keeping the window surface warm.

InnerWindows Eliminate Drafts
InnerWindows=16% Reduction in Infiltration

InnerWindows dramatically minimize infiltration of air from around the existing window.  This draftiness is actually a larger source of lost energy and interior discomfort than U Factor.  We have tested the effectiveness of Capitol InnerWindows by hiring an independent energy auditor to conduct Blower Door Tests on a home in which we have installed InnerWindows.  

Blower Door Test uses sophisticated technology to pressurize the home and calculate air infiltration.  With InnerWindows in place, air infiltration in the home was reduced over 16%. That translates into a much warmer and more comfortable interior.

Click Here for Air Infiltration Test Data

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