Indow Window + single pane performance numbers are from independent testing conducted by Portland State University's Green Building Research Lab.  Actual performance numbers will vary.

Air infiltration (lower is better)
The tight seal between the Indow Windows' spring bulb and your window frame provides industry leading performance. 

R Value (higher is better)
An Indow Window combined with a single pane window provides 94% of the thermal insulation (R-value) of standard double pane replacement windows.

Noise Reduction
When placed over an operable single pane window, Standard Indow Windows dampen noise coming through the window up to 10dB, which equates to a 50% noise reduction.  Acoustic Grade Indow Windows reduce noise coming through the window by up to 18.9 dB when placed over an operable single pane window,  equivalent to a 70%+ reduction.  

Please note, overall sound reduction depends on sound coming through walls and doors. The reduction will not be as great when Indow Windows are placed over double pane windows.  Noise coming through walls, ceilings, and doors will diminish the overall noise reduction.

Lead
Homes built before 1978 likely have toxic lead paint hidden in the walls.  Indow Windows do not disrupt your walls so lead is not a worry.  If you replace your windows make sure your contractor follows EPA regulations to contain toxic lead paint. 

Condensation
Indow Windows typically eliminate or  dramatically reduce condensation on single pane windows.  You can read independent analysis of condensation issues here and here.

Please note, Indow Windows larger than 8 square feet have a very discreet safety strap that connects the Indow Window to the window frame. The safety strap is hidden on the outside of the Indow Window and attaches to the frame with a single screw.