April 2011: Attics Flats
At first glance attic flats may seem to be one of the easiest configurations to retrofit. Yet there are some major considerations that need to be addressed at the onset. As the Guidelines suggest, one needs to keep in mind why they are being kept as a flat or being sectioned off as part of a conditioned attic. Some other issues would be how complex they are: a shed or dormer needing access to a main attic or an enclosed space with no dedicated area for venting. Additionally, the pitch over the flat may drive recommendation for accessibility and dense packing options.
Auditors and contractors should be aware of all the interior features that may be present and needing to be evaluated and addressed. Most of these will fall into the following category: all chases, drop ceilings, soffits and drop-down bulkheads, stairwells, open wall cavities, slant & floor systems, wall plates/ penetrations, combustion vents and chimneys, adjacent walls or floors that are off-set, heat producing items such as fans & lights and distribution systems of pipes and ducts.
Whether it’s an unconditioned or a conditioned attic one must realize that many of the vertical pathways, if left unsealed, can or will be connected to horizontal pathways within the building and ultimately contributing to series leakage. This explains why after conditioning an attic and increasing the total conditioned volume of the entire space (without doing any sealing work on the attic flat) does not effectively diminish the existing CFM limits within the building.
When addressing ventilation, one should visualize the plan for the height of the additional insulation level and thereby make a determination as to the need to extend/replace the existing baffles. Leaving the baffles shorted should not be the determinative cause for a diminished installed R-value by installers. Correspondingly, R-values on proposals should be noted as an “installed” value and not a resulting “total” R-value. Denoting an installed R-value takes very little of the subjectivity out of the process. Where designating it as a resultant R-value is open to personal interpretation, confusion and possible fraud. The R-sticks should be at least 18-20 inches in length and should be placed at the top of the existing insulation level.
Insulation choices should be evaluated with respect to wind-washing and being disturbed (blown way if a whole house fan is there or is one is being planned) – insulation surrounding the fan should be batts and not loose fill. Batts can also be used as effective dams, barriers and small plots to hold necessary marking flags if no framing is in close proximity. Installed insulation levels should be an inch or more than what is called for in the contract in order to still be an effective settled depth within the one year warranty period.