Sunday, April 15, 2012

Insulation requirements and changes in Modern Day construction of custom homes


Modern Day Construction for custom homes Part 3

In today’s modern world of construction things are changing year to year faster than they did decade to decade in any other previous time period. In this multi part series I will traverse through an entire house starting with the foundation and working my way up to the roof and then to the finishing’s. I will explain what has changed in the last twenty years in custom home building.

One thing that you should be able to take away from this is how important it is to not just hire the right general contractor to build your custom home but how important it is to hire one that is up on today’s building methods.

Here are some changes that have come along in the last 20 years alone;

Insulation

Twenty years ago all exterior walls were insulated with pink fibre glass insulation. Attics were done with R-35 to R-40 blown-in insulation or pink fibre glass insulation that was laid in multiple layers. Interior walls were packed with pink fibre glass insulation to try and keep sound from traveling from one room to another.

Today there are so many choices to be considered;

Blown in insulation in the attic has now become R-50 to R-75. You achieve this by applying 2” of spray foam to the attic side of the drywall that has been attached to the ceiling, then installing your blown in insulation on top. The spray foam acts as your vapour barrier as well. A lot of ceilings that have cathedrals or tricky sections that you will have trouble venting are now completely insulated with spray foam; you can easily achieve R-40 or better in these areas.

Walls now can have blown-in insulation installed in the wall cavities. The blown-in is held in place with a mesh that is installed first. Then once the blown-in is installed the vapour barrier can be stapled up. Blown-in insulation has a higher R value than normal fibre glass insulation because it is able to be more tightly packed into the wall cavities; this slows down the air penetration into the home from the outside world.

Foam board is being used now to add extra insulation to the inside of the wall. It has a reflective surface on one side that once placed into toward the house, will help allow the heat to be reflected back away from the walls. The foam board also acts as your vapour barrier. All you have to do is use tuck tape to tape the joints. A little acoustical caulking on the top and bottom of the wall before the foam board is set in place helps give it a good seal as well.

Rim joist which were always the worst place to vapour barrier and insulate are now spray foamed between every joist cavity. This helps give the house a nice tight seal.

Spray foaming around all doors and windows is the norm now, helping give windows a draft free feel. It seals around the windows to stop all air flow and air penetration.

Spray foam is also used in larger quantities throughout the home. It is used especially in the ceiling areas where there is little or no air flow. Rim joist, garage ceilings and anyplace in the outside walls that has a post or obstruction that doesn’t allow enough wall insulation to be installed. Spray foam is used to insulate overhangs that extend out away from the floor below, especially when there is plumbing pipes that need to be kept warm and protected. Some houses are completely insulated in spray foam from top to bottom. Filling a 2x6 wall cavity with spray foam can give you up to an R-35 rating. With the added value that there is little or no air penetration through the wall. Any area that has been spray foamed does not require a vapour barrier, the spray foam acts as its own vapour barrier which helps in places that are tricky to reach or tape properly with plastic and tuck tape.

Today interior walls are filled with a number of different materials to cut down on sound and noise traveling from one room to another. Roxall is sometimes placed in between the studs. Roxall is a fire resistant product that is made out of a paper base instead of a fibreglass one. Also they use a sound absorbing material that goes on underneath the drywall to help absorb vibrations. Ceilings are not only filled with Roxall but they use a drywall metal track to help isolate sound and vibration from floor to floor.

Polystyrene foam is used on the outside of the exterior walls. It comes usually in 2 ft by 8 ft sheets and varies in thickness from 1” up to 2”.  They are placed on the outside of 2x6 wall studs and often are used instead of OSB or plywood. Polystyrene is also placed under the concrete slab in the basement. It is also placed in spots that conventional insulation will not work well and places where spray foam will not be able to be installed at a later date.

Insulation is one of the places that has the greatest room for change and is also one of the area’s that has changed dramatically in the last twenty years. Recent changes to building codes are forcing manufactures to come up with new ways to insulate in the same space capacity. Newer fibre glass insulation is coming on the market that will help raise the R value to meet new codes.

Look for part 4 coming soon...

Rob Abbott
Operations Manager
Village Builders Inc.




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