Energy Efficient Sliding Glass Door and Window Upgrades in CT

An insulated wall may have a rated R Value of R-13, but a typical sliding glass door or window may only have an R value of R-2!  Obviously, the door or window is a big energy loser. 

Energy Efficient Sliding Glass Door and Window Upgrades in CT - Image 1Why The Drafts?

Many people complain of drafts in the winter time.  Door and windows may leak and if they do, that can be part of the draft you feel.  But because the glass is cold, it creates a "convective loop".  This is how it works - warm air inside contacts the cold glass, which then cools that air.  Cold air is heavier than warmer air, so the cold air sinks to the floor and runs across the floor.  Along the warmer interior wall the air warms up and rises to the ceiling, across the ceiling, back to the glass, down to the floor - you get the idea.  So you're sitting in the room with the big glass surface and you feel a draft.

Another reason sliding glass doors can feel so cold is radiant heat loss from your body.  Heat moves from hot to cold.  Heat radiates off warm surfaces to colder ones.  Your body is 98.6 degrees and the cold glass is much less.  So when you are near the glass, heat is drawn off your body by the cold glass - making you feel cold.

Understanding Air Leakage

As far as air leaks through a door or window, there could be air leaks from the door or window not closing tightly - which everyone can understand.  But another problem is the shim space around the door.  A 6 foot sliding glass door will have an opening framed in the wall by the carpenter who built the house that measures 6 foot two inches.  This gives room for the jamb (frame) of the door, and room to shim it level and plumb upon installation. 

The remaining space of about 1/2" to 3/4" all the way around the door is commonly loosely filled with fiberglass insulation.  Fiberglass lets lots of air in.  Any air that gets around exterior trim or through the siding can come in AROUND the door in the shim space.  Now it just has to get around the interior trim between either the wall and trim or the trim and frame - and it's in the house.  Older homes may have no insulation whatsoever in this shim space. 

So there's four reasons you feel cold due to sliding glass doors - or any window and door.Energy Efficient Sliding Glass Door and Window Upgrades in CT - Image 2

  1. Cold glass - heat from inside your home radiates to the outside and is lost.
  2. Convective loops - The cold glass cools the air inside and makes it move
  3. Air coming around the door/window frame through the shim space
  4. Air leaking through a door/window that doesn't seal properly.

In addition, glass doors tend to let in a lot of heat during the summer.  Like a greenhouse, glass lets in solar radiation that heats up the house.  Air conditioning is run more often as a result and that just costs more in electricity.

Clearly, upgrading to a high performance sliding glass door - or any window and door, is a great idea to make your home more comfortable and save energy.

Qualities of a High Performance Glass Door

          1. Low E glass: E stands for "Emissivity".  This means the glass will let in visible light but block much of the heat - that part of the light spectrum that transmits radiant heat.  A metallized coating is applied to the inside of the glass, (think of sunglasses) that accomplishes this.  Low E glass is slightly tinted.  Low E glass will also prevent much of the heat flow OUT in the winter, giving you a benefit in summer AND winter.
          2. Multiple panes of glass: By having two panes of glass, the Low E coating can be applied to the indsides of each, and an air space can be formed between the panes.  This air space helps to insulate the glass from heat passing through.
          3. Argon filled glass: The space between the glass can be evacuated of air and argon gas can be used instead.  The argon will not transfer heat through it as much as air will, giving you an added defense against heat transfer in winter and summer.
          4. Vinyl frames: Vinyl lasts. It doesn't rot, warp or ever need paint.  Perfect since the outside of the door gets wet all the time.  You'll save a lot on maintenance and your doors and windows will look good all the time!  A door or window with a metal frame is highly energy INefficient.  Metal, usually aluminum, is hundreds of times more themally conductive than other materials used for maufacturing doors and windows - the worst!  The frames will always be very cold inside in cold weather. 
          5. Air Sealing and Insulation: When a new door or window is installed, the shim space should be air sealed and insulated with foam insulation.  Expansive foam insulation fills all the gaps and won't let air around the frame - in or out.  Foam is also a great insulator for this space.  When installing "replacement" windows", the new windows are installed inside the existing frames.  Since the same interior and exterior trim are used and never removed, the shim space is never exposed.  In order to foam the shim space around the frame the interior trim must be removed.  Doing this means it may have to be replaced if it cracks - and at the very least nails holes will have to be puttied and the trim repainted.  It's worth it.  Those windows will be there a long time - do it right.
          6. U Values: You can't just go by the door or window brand name.  Just as Chevrolet makes some great cars, they make others that are less great.  Many window and door manufacturers make "Good - Better - Best" products.  You have to look at the U Value on the label.   Each door or window has a U Value.  The lower the U Value the better.  A VERY energy efficient window will have a U Value of .3.  A poor U value may be .5 or higher.  The U value is the inverse of the R value.  To find out the R value of a door with a U Value of .3, we divide 1 by the U Value.  So 1 divided by .3 equals an R value of 3.33.  A window with a U Value of .5, has an R value of R2.  So a window with an R value of .3 is 65% more energy efficient than one with a U value of .5.  Install the door or window with the lowest U value you can.  Of course better, more energy efficient windows cost more, but it's well worth it.

Energy Efficient Sliding Glass Door and Window Upgrades in CT - Image 3Dr. Energy Saver can help you with all your window and door needs in Hartford County, New Haven County, or Fairfield County - and anywhere in the state of Connecticut.  We'll make sure your new Sliding glass doors, windows, and doors are as energy efficient as they can be.  We're you source for anything your home needs to be comfortable and efficient including air sealing, insulation, duct repairs, high efficiency heating and air conditioning and water heating, radiant barriers and lighting.  Call us today for a free home evaluation and estimate. 1-800-328-1081

Service Area
Free Quote