Friday, 29 July 2011

Fiberglass Batts – Labeled vs. Installed Performance

Oak Ridge National Laboratory research shows that “perfectly installed” batts lose 11% of their R-Value, and that “commonly installed” fiberglass batts lose 28% of their labeled R-Value.
This study confirms tests conducted 20 years ago by fiberglass manufacturers, and reveals the surprisingly large disparity between the labeled R-Value and the installed R-Value of fiberglass batts

What Was Measured:
The R-Value results presented here are the clear wall R-Values, which AndrĂ© Desjarlais of Oak Ridge explains, “includes the studs, top and bottom plates, shethings and exterior facade… It does not include additional structural components around details such as corners, windows, etc.”

“The clear wall R-Value… represents the area of the wall containing insulation and only the necessary structural member away from all interface details.”

“To address the number one wall research need… whole wall performance was ranked by 270 private building industry contributors as the most important public sector R&D need to accelerate the development and application of energy-efficient building walls.”

Full-size walls were constructed and tested to determine their thermal conductivity.

What Did They Find?:
The highest tested R-Value for “R-19” labeled batts was R-17.4 for batts before they were installed.
From there, the test results dropped to R-17 and then R-13.7

So the question is: Can’t R-values be used to compare insulation systems?
R-values are a good starting point – but they are the results of small, meticulously prepared laboratory samples and do not necessarily reveal how an insulation system performs once installed in actual buildings. Different insulation systems with the same laboratory “R-value” can deliver much different levels of comfort and energy efficiency

Friday, 22 July 2011

Bonus Room Floor Insulation

Drop Box / Hot box or insulation between your floor joists

Providing heat and proper air flow to a bonus room floor can present many challenges, with most rooms being more a liability than a bonus. A careful look at several issues will provide a better understanding and a possible solution to this problem.

The problem:

  • Bonus rooms have five cold surfaces. A typical heated space has from one to three walls adjacent to unheated space. Bonus rooms have cold knee-walls, ceilings, floors, and an outside wall.
  • Bonus room insulation is frequently missing ... after all; the walls, floor, and ceiling are "indoors".
  • Bonus room knee-walls insulation is typically open on the backside, exposed to ambient attic air ... Insulation R value is always diminished by air infiltration.
  •  Knee-walls often lack a top or bottom plate, which means drafts, can move freely between the insulation and the drywall
  • Bonus room floors are typically insulated from the garage below. The insulation is placed against the garage ceiling with an open-air gap against the bonus room floor. The air gap frequently connects to the band area, attic, or garage air leakage produces a cold floor.
  • Heating system duct-work is normally placed in one of these cold spaces and with space constraints is typically not insulated properly. Heat loss from exposed ducts can be excessive. The bonus room demands efficient heat delivery increasing heating cost for home owners
  • If the floor in your Bonus Room is not fully sealed, there is a strong likelihood that contaminated air, gases, and more can penetrate your living space.

The solution:

Insulation performs best when totally encapsulated — that is, covered on all six sides, as it is in a standard exterior wall. Remember, the main purpose of insulation is to enclose the living space in a thermal envelope.
Spray foam insulation installed between your floor joists in your Bonus Room floor is the only material that will create an effective thermal barrier from obstructions such as wiring and plumbing, ductwork, and narrow or wide joist spacing.
Insulation should always be placed against the conditioned surface, air gaps allow air washing.

Open floor joist cavities should be blocked to prevent air movement through the floor insulation

Heating ducts should be placed against the wall or the floor above and should be well insulated.

Builders need to weigh the relative costs of dropping the ceiling on the bonus room as to Air seal it and insulated with Spray Foam