What to look for in a great builder – Building Envelope

Building Envelope

You can get the best, most energy efficient, and comfortable heating system money can buy, but if your  building envelope is not built properly you will never receive the fullest potential of the unit you purchased.

Did you know we have customers who have reported to us that their electric bill during this past cold month with subzero temperatures was slightly over $100 for their four bedroom 1750 sq ft home and another customer reported having an electric bill of only $300 for their 5,500 sq ft home. Both these homes only had an electric heat pump as their sole heating source?  This is because James Monroe Homes are built with a very tight building envelope.

First we need to make sure all the air from the heating system is getting into your home.  Many times due to poor installation the ducts will leak.  To limit these leaks we make sure all the ducts are sealed to the boot, taped, and zip tied.  Every duct is a home run which means it is a single duct line from the furnace to the room.  We also make sure the ducts are caulked to the drywall because this gap will cause air to leak.  Once we know all the air is leaving the furnace and arriving in the house we have to make sure the building envelope does not allow the air to escape.

Building envelope - James MonroeThink of your house as a balloon.  We want to keep the warm air inside and the cold air outside.  If the balloon has lots of holes in it, it does not matter how much warm air we blow into it, that air will just leak outside.  A well-built building envelope will seal up all those holes and traps the warm air inside and restricts the cold air to outside.

Insulation is very important to your home’s building envelope.  Insulation does not stop the movement of air it only slows down its movements and ability to travel.  Insulation has to be properly installed to work effectively.  When insulation is compressed it loses its ability to slow the air movement down  This is why James Monroe Homes cuts the insulation to fit each stud cavity, around pipes, and wires to insure the stud cavity is filled completely without the insulation being compressed and compromised.

To completely stop the air flow we need to utilize six sided air barriers for all insulation.  Typically this would be a wood stud on the left, right, top, and bottom of the insulation.  Then we would put OSB sheeting on the outside and drywall on the inside.   All these materials are consider air barriers.  James Monroe Homes takes the extra step to ensure we have a six sided air barrier on the entire building envelop. When we have knee walls in the attic, angled ceilings, and behind tubs one or more of these sides are not air blocked.  So we have to go in and put in an air barrier to protect the integrity of the building envelop.

There are many steps we take in the attic to ensure maximum insulation and minimal air leakage.  On a typical house the lowest part of the roof where it is over top of the wall is only 7” tall.  In order to get a full R-38 insulated value you need 13”.  So we build up the trusses or roof system at the edge of the exterior wall to allow for a full 13” of insulation over the exterior wall.  We also seal every hole that is drilled in the top plates for a pipe or wire to go into the attic with a fire rated caulk.  We seal the attic access panel with a weather strip to prevent air flow from leaking around the opening.  We insulate the attic panel and build up the attic plat form to ensure that every area inch of ceiling has a full R-38 insulation value.

Before we start a new James Monroe Home we hire a HERS rater to review our plans.  It is his job to size the HVAC equipment based on our insulation plan, window schedule, and other factors.  We will have this third party inspector review our plans prior to start of construction to ensure we have thought through every energy efficient detail of the house.  He will then walk through the house when we have insulated but before drywall to verify all insulation is installed correctly, has six sided air barriers, and our building envelope is solid.  Once the house is complete he will do two test.  The first test will test the duct system to ensure there is less than 5% air leakage in the duct work. The second test he will pressurize the entire house to verify the building envelope is tight and only allowing a limited amount of air to leak.  If we pass both these final test he will rank our homes with a HERS Score.  Our homes have to score at least an 85.   A new home built to the current energy code will score 100 and your existing home will score 120 or greater.  This means James Monroe Homes are at least 15% more efficient than other new homes and 35% more efficient then existing homes.

Make sure your windows are locked, your furnace filters are cleaned, and there is proper weather-stripping on your doors.  These small things will also have a huge impact on your utility bills.

It is not an accident that our customers have some of the lowest utility bills in the area.  They have them because we took the extra steps and care in building their home to have ducts that do not leak and a building envelope that keeps the warm air in.

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