Downtown apartments in a desirable part of a city can fetch high rent prices, especially when multiple people are interested in renting a specific unit. Some potential tenants, however, are turned off by the noise that comes with living in a metropolis. If you're a landlord with a downtown apartment to rent, installing double-pane replacement windows in your unit can reduce how much noise is heard from inside your unit. Upgrading the windows could help you attract more prospective tenants -- and possibly command a higher rent for the place.

STC Ratings Measure Noise Insulation Levels

How well a specific building material insulates against noise is quantified by its Sound Transmission Class (STC) rating. Almost every building material used in construction, from ceilings and floors to doors and windows, has an STC rating.

The STC rating scale is exponential, so even a moderate increase in a material's STC rating can provide significant improvements. According to Jeld-Wen Windows & Doors, an increase of

• 2 points is not noticeable
• 4 points is "clearly perceptible"
• 10 points reduces noise levels by 50 percent

Single-Pane Windows Have Low STC Ratings

Of all the building materials used in an apartment, windows have some of the lowest STC ratings. For reference, Jeld-Wen notes that a typical exterior wall has an STC rating of 36. Single-pane windows, which are often used in rental units because they're inexpensive, only have an STC rating of 24 to 26, according to TheWindowMan.com.

At this low rating, normal speech is clearly understood on the other side of the building material. The sounds of trams, car horns and sirens from the city's streets will come into an apartment with single-pane windows loudly and clearly.

Double-Pane Replacement Windows Significantly Reduce Noise Levels

Double-pane replacement windows provide more noise protection than single-pane windows. As Better Homes and Gardens explains, double-pane replacement windows usually have glass that's between ¼- and 1-inch thick, and there is a layer of air or argon between the glass. When sound travels through the glass and air, which have different densities, the waves are disrupted. Thus, less noise passes through.

TheWindowMan.com's figures list double-pane windows' (which are also known as double-glazed windows) STC ratings between 31 and 33. When laminated glass is used, the rating improves even more, to between 35 and 38 -- on par with an exterior wall's rating.

Triple-Pane Windows Provide Less Sound Insulation

Triple pane windows, counterintuitively, often provide less sound insulation than double-pane replacement windows. TheWindowDog.com notes that triple-pane windows have smaller air gaps than double-pane models, and triple-pane replacement windows sometimes have thinner pieces of glass.

Although there are more layers, they aren't as thick. Sound waves are able to pass rapidly through each layer, rendering the windows less effective at blocking out noises.

Soundproof Windows Are Effective But Expensive

Soundproof replacement windows, another option, provide excellent sound reduction. They can cut noise levels by 90 to 95 percent.

These windows, however, are much more expensive than double-pane replacement windows. They're rarely, if ever, installed in rental units because their price usually exceeds any potential increase in rent.

If you're looking for an affordable way to increase your downtown rental unit's appeal, contact a window company about installing double-pane replacement windows. While they aren't the only type of replacement window, they'll reduce sound better than many triple-pane windows, and they'll cost less than soundproof options. Most importantly, double-pane replacement windows will reduce the noise levels in your rental. They could block out over half of the street noise that comes into your unit -- which would make it much more attractive to prospective tenants.

You can click here for more info on replacement windows for your downtown apartment.