Guy's Corner

Every month LEAP's Residential Energy Services manager Guy Caroselli shares his perspectives and expertise on aspects of home energy efficiency. He selects topics that have been recurring issues for homeowners and contractors in LEAP's programs. Home energy professionals will find Guy's Corner a practical resource and reference point. 

March 2011: Bath Fans

The addition of bath fans should always be considered as part of an energy retrofit. Even if there is no evidence of a moisture issue or the bathroom does not have a shower or bath, they can provide potential exhaust ventilation should the building fall below 70% of the Building Airflow Standard. Sometimes it may be as easy as placing them on a programmable timer that replaces the standard wall switch. Bath fans are rated in CFMs and should be sized not only with respect to the size of the bathroom but planned duct run and corresponding length. The longer the duct, the more restrictions, what side of the house it exits on, the type of closure unit and the pitch of the duct all will affect the actual CFM exhaust capability. Fans can be located on walls when ceiling applications prove to be difficult.

Fans are also rated in Sones for their sound rating with 1 being the quietest and 3 usually being the loudest. If there is going to be a light and a fan within the same housing, it is always better to have them on a separate switches - especially during the winter when one may NOT want to exhaust moisture. All fans, whether existing or new, should be ducted to the exterior of the building with a continuous insulated flex duct that has excellent inner and outer sleeve connections to the exhaust port and the closure body. The plastic exhaust port should be placed with the flap closed and well sealed to the housing so as not to leak or be pulled off. Sometimes the extra holes in the casing of the fan can be metal tapped for improved air flow and the body of the fan should always be sealed to the adjoining surface.

One should always think about where they intend to exhaust the duct before the fan is set in the ceiling.  There should be no restrictions for the first 3-4 linear feet of duct run. One may need to use and adjustable elbow or 3” to 4” expander to make a smooth transition. There should be one dedicated duct (no teeing or joining) for each fan unless there is a centralized unit with individual passive grates located at various source points located around the house. If it is problematic to get the fan completely ducted to the exterior getting the termination point as close to an existing vent and on the leeward side of the building would be preferable. There should be good exterior closure unit; ones that have a floating shuttle (these are about 14” in total length and just the body can be used for through the roof applications) seem to work best at minimizing the exchange of conditioned and unconditioned air. Existing fans should always be check to insure the do terminate outside of the building shell and are in good working order. All fans could be checked with a pressure pan or flow hood for actual CFM capacity should the need arise for determining mechanical ventilation capacity.

April 2011: Attic 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.

May 2011: Conditioned Attics

The decision to create a conditioned attic space can be a viable solution with regards to much of the housing stock and existing configurations we find within our mixed humid climate.  The four points referenced in the Guidelines (4.6.1) should always be considered. Sometimes the driving force is the mere fact that the space contains: a furnace, air handler, or large amounts of duct work that are presently outside of the existing pressure and thermal boundary. It was recently found in two test houses (Knoxville, TN) where one attic was conditioned and one was not, that the unconditioned/vented attic experienced average daily temperature swings of 40-55 degrees during the summer and 25-30 degrees during the winter. No matter how well sealed or insulated the duct work is, it cannot overcome these kinds of temperature differentials.

The approach should not be simply to foam the entire attic space. Sectioning off the space to create a newly dedicated, abbreviated, conditioned zone and leave the accompanying unconditioned flats or wings left as they are should be evaluated. Obviously erecting a fire proof wall or envelope, satisfying make up air, and addressing all code issues should be figured into the cost/equation. A recent meeting with a county code official revealed they all generally take the position to defer to the manufacture guidelines and specifications for compatible ignition barriers and coverings. Relevant permits for: erecting a wall, changing out to solid fuel appliance, or providing acceptable make up air after reconfiguring a space may apply and the onus is upon the contractor to be aware of Virginia Construction Code (section 108). Often times because of the existing pressure and thermal boundary is: very convoluted, extensively floored, has not been sealed, and is hard to navigate that conditioning becomes the obvious and only feasible strategy.

When conditioning an attic it is paramount that it is completely isolated from the outside and other unconditioned areas. Properly identifying the newly reconfigured pressure/thermal boundary and insuring that it satisfies the three guideline requirements is essential in justifying and actualizing the added retrofit cost. Making sure that the foam does not simple wash over an existing batt on the flat, that end floored ceilings bays have been addressed and knee wall junctures have been blocked of are only a few of “checks” in the application process. Sealing major penetrations on the ceiling plane and insuring that any vertical chases are not connected via series leakage to horizontal chases would be critical in providing a quality installation. Blower doors with smoke sticks, zonal and pressure diagnostics can also provide valuable feedback about whether the newly conditioned space is  disconnected from the outdoors.

June 2011: Vented Crawl Spaces

Conditioning a crawlspace when living within in a mixed humid climate can be one of the largest factors in moderating and affecting indoor humidity levels. Obviously one of the major determinative factors is if a persistent moisture condition exists already.  One needs to make the call with a number of considerations in mind: can the source be diminished with a minimal financial investment, is it practically feasible to do so, and is one confident that the remedy will in fact work? The other health and safety consideration is the scenario one will be in effect creating. If there are combustion appliances in the vented or semi conditioned crawl space and one plans upon a total conditioning, then allowance for proper make up air must be taken into account (50 cubic ft for every 1,000 BTUs).This must always be built into the work scope on the front end and in proper sequence. If the moisture source is too great, then the pressure thermal boundary should remain as the floor and the space be intentionally vented with humdistatically controlled vents. Sometimes by adding a sump pump to the low spot in the crawl and diverting most of the ground source moisture there will be enough. There are Dranjer covers that can be added that will allow moisture to go one direction no vapor or radon gases to pass through in the other direction.

If the crawlspace is relatively dry and connected to an existing basement then the three exterior sides should be done. Depending upon the size of the crawlspace walls, sometimes doing the exterior can be one half or one third of the area when compared to the floor area. This approach either initially or upon retrofit, can reduce the insulation costs and remove the barrier from having to work overhead. That being said, if the walls are very tall only the first foot below the frost line and all area above should be foamed. If it is a separate zone under the dwelling, then all crawlspace vents should be blocked and all accesses and hatches addressed. If balloon framing exists and the wall cavities are open to the crawl then they should at least be blocked off or better yet utilized to dense pack the wall cavities. If the space is known to remain dry then open cell could be used but if there is any chance of exacerbated moisture levels or conditions then closed cell should be employed. The vapor barrier should be installed with the few seams possible and sealed at all the penetrations and follow best practices. The thickness of the vapor barrier can either be increased or decrease depending upon access, use, and amount of resultant moisture conditions. In any case humidity levels should be monitored and kept below levels where the dew point and condensation could occur. All other installation considerations should follow the Guidelines section on: Floor area and Crawlspaces.

Floor areas come in all kinds of configurations and locations within existing buildings. Sometimes it is not uncommon to have four to five separate areas in one building alone: conditioned basement, attached crawlspace, floor over a garage, slab, and open floor (like a breezeway or converted porch). The ensuing recommendations might be very different for each area if in fact they were all being addressed. Some considerations obviously are:

·        Location of heating plant and distribution system at present and future

·        Area’s connection to  any existing conditioned area already

·        Space limitations under, around, on top, or inside of area and joist cavities

·        Recommendations driven by: moisture, noise, smells, and material itself

·        Budget constraints of treating area because of its’ location, size, existing surfaces and future plans

Seldom would I recommend insulating a floor area unless it had a dedicated heating system situated above the PT boundary as with a wood stove, space heater or electric resistance heat. Most problems occur because the insulation is not present, is sitting 3-6” off the floor or is being subjected to temperature extremes or wind washing as with open or soffitted areas. When direct inspection is impossible or impractical one should look for small holes up in side of enclosed space. A lot of information can be gathered from having a 12” piece of hanger on hand: size of joists, direction of joists, location of insulation, amount of insulation, type of insulation, quality with which it was installed, if blocking is present or is needed.

Areas to pay particular attention to are areas over garage ceilings that contain duct work or areas between floors that are connected and in communication with other open or vented areas like porches and vented soffits.

Some companies have been experimenting with just doing the perimeter of the garage ceiling if there is some insulation in place to stop the short circuiting at the perimeter. Some spaces are just going to be cold as in uninsulated slab floors with no exterior foundation insulation and the only solution is to build up the floor or add heavy padding and carpeting.  Remember, one’s feet are almost always in contact with the floor and if your feet are cold you are going to be cold.

If there was a single concept that should be ingrained in all contractors that work directly or indirectly with Home Performance it would be getting the pressure and thermal boundary correct.  Whether it is identifying it correctly on the front end of the assessment or in the reconfiguration process after building an actionable work scope or as work proceeds, it is paramount to get it RIGHT. This is the main reason it ranks as the first item on my Lucky 13 List of prescriptive areas to apply to all buildings. Though I refer to the three criteria as : complete, well-defined, and, aligned with one another; John Tooley and the gang at Advantage Energy call them by the three “Cs”…COMPLETE,CONTINIOUS and CONTIGUOUS. A couple of excellent articles can be referenced in the past issues of Home Energy March/April and May /June 1999 (these were handed out during the first Teaser session). It may seem like a simple concept to convey but to actually understand and SEE it takes experience, time spent looking at a lot of buildings, and, what I refer to as “spatial referencing”….If you were good in Geometry class this helps immensely.

Remembering that Home Performance could best be described as three main strategies:

1.      To treat the house as a system

2.      To build/retrofit according to climate (mixed humid)

3.      Control the movement of: air, heat and moisture.

Realize that these three barriers do not completely block they simple retard the flow of this air, heat and moisture. It is the job of the Building Analysts to identify them, the contractor’s job to put them in place and QA’s job to insure they are there and working properly. By accomplishing these goals we all serve a unique part to insure the clients actualizes greater: comfort, health, safety and savings. “The objective is to restrict air, heat, and moisture movement at its source, reducing their entry into the assembly or conditioned space. This practice will help reduce air infiltration, hidden condensation, mold growth, and rot and to maintain installed R-value. “John Tooley Home Energy May/June 1999.  We can dive deeper at some other time.

Next month in Guy's Corner: Walls Inside and Out