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Residential Energy Efficiency Blog

Friday, August 21 2020
5 Reasons Your New Windows Are Drafty (#1 Might Hurt)

It is not uncommon for homeowners that have purchased new replacement windows to be disappointed the next cold season because the new windows still seem drafty after installation. 

Here are five reasons why your new window replacement investment might leave you asking: 

Why are my new windows drafty?


1. The Windows Were Not the Draft Source to Begin With

Often times windows get the blame for everything when it comes to home comfort.  This is somewhat confusing when considered through the lens of physics but not so much when considering the psychology of the window. 

The window is the part of the wall that we can see through.  If we hear something on the other side of a wall we assume that we hear the noise through the window.  If it is cold or hot and sunny, we can identify with the temperature by what we see.

On the other hand, physics and pressure and airflow dynamics tell a slightly different story.  There is no doubt that a window can be a source of comfort woes or energy in-efficiency, but so can hundreds of other points around a house and often times the worst offenders are places that you would not ever have imagined.

2. Understanding Stack Effect

The stack effect can be understood by thinking about a wood burning fireplace in a house.  At the base of the fireplace we place the wood and light the fire.  At the top of the fireplace is the chimney with a stack that usually rises up and above the roof for the hot smoke and ash to billow out.  In every fireplace a pressure dynamic develops when the fire is lit.  Stack effect diagram

At the base of the fire is the negative pressure.  A way to think of it is the fire sucking up oxygen to keep the flames ignited. 

The opening at the top of the stack is the positive pressure.  The smoke rises up and heads straight out. 

This stack effect pressure dynamic happens inside your home too.

Myths about new window drafts and comfort solutions can be unlocked by understanding the stack effect.  It is best to search at the basement level (base of the fire - sucking outside air in) and the top floor ceiling level of a house (top of chimney where conditioned air is looking for a way out!).

3. Fireplace Flue/ Recessed Lights

If you just put brand new windows in and you still feel drafts, then look around a bit.  One easy way to find drafts is to look for the "gateways" to the outside. 

For example, one out of every five customers that I do an energy audit for do not have the flue shut on their fireplace chimney which is a huge gateway to the outside.  

Recessed lights are also gateways to the attic (outside) and if you have them and you had your windows replaced and your draft problem did not go away - consider it as a possible source of your issue.

Recessed lights are the source of home drafts

4. Improperly Treated Crawl Space/ Basement

Open crawl space vent.If the construction style of your home is on a crawl space that is open, then you might experience high drafts.  An open crawl space will allow unconditioned air into the the crawl space and unless there is a proper pressure boundary separating the foundation area from the room above, then drafts will surely occur through the floor.

If you have a full basement it is very likely that the rim joist in any finished or unfinished area has not been properly air sealed and this will allow air infiltration in the basement area that will cause drafts through walls and floors into the living space above.

5. Improperly Installed Windows

Another possibility for drafty new windows, however the least likely, is that the windows were installed improperly or worse yet, not caulked and sealed.  Even if this is the case, it would still be difficult to make a draft problem worse with new windows even if the windows are incorrectly installed due to pressure dynamics in a house.  It is important to note however, that basement windows and windows on the second floor could be susceptible to leakage if not properly installed and sealed due to higher pressure.

What can you do about this?

A great way to deal with the issue of drafty new windows is to have a comprehensive home energy audit performed.  An energy audit includes a blower door test.  A blower door test is an air leakage test on your house.  It is a large fan that pulls air out of the house.  When the air leaves at the front door new air replaces it from the holes and cracks around the house.  You can actually go around and feel around new or old windows and feel around a recessed light and see for yourself that what I am saying is true!

air leakage testing new windows



Get an  energy audit to test drafty windows and other leaks in your Maryland home for $100 today!

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