I recently came across a new/old article concerning the common myths about energy efficient building construction, renovating for energy efficiency and home maintenance for energy efficiency. The article was written by Martin Holladay (Editor, Energy Design Update) and appeared in the Journal of Light Construction in June 2008. I found it in the on-line archives of Remodeling Magazine.
The article touches the scientific surface of several construction/remodel upgrades builders and homeowners are encouraged to do by writers in the print/on-line media (including the professional media), and through the marketing efforts of product manufacturers. Holladay debunks the myth and promotes the scientific application of a method or means of increasing the energy efficiency of a home/structure. While the article focuses on “northern” building climates, there is much here for those of us in Florida coping with the peculiarities of a hot-humid storm dominated building environment.
Goto “A Close Look at Common Energy Claims” by Martin Holladay.
(1) Window Replacement – as Holladay points out, window replacement is often advertised as the way to beat the energy-bill. Given the current costs of high-performance windows (limited availability), there is rarely a pay-off here for the homeowner. Most advertised energy-efficient windows do not qualify for the 2009 tax credits, and the tax mechanism of tax savings is too often misrepresented. Additionally, high-performance windows (low-e, low U-factor) when retrofitted to an existing structure will lead to long-term health risks to the occupants (when other functioning elements of the home are not upgraded at the same time). The original home design (especially the mechanical, or HVAC, design) did not include such radical changes to the building envelope – the home was originally designed to “breathe” differently. There are greater benefits and cost recovery time-lines from radically upgrading a home’s HVAC than changing out its windows. Additionally, windows must be installed properly or their touted efficiencies will not be realized (poorly installed, they will lead to efficiency losses instead of gains), and other health and safety risks will be introduced to the home environment.
(2) Housewrap – when installed improperly housewrap can turn a home into a moisture/mold trap. If you are installing this yourself DIY, or have hired a contractor/subcontractor to install housewrap for you, make certain they are following the manufacturer’s recommended procedures and fastening schedule for that particular product. Housewrap is an awesome drainage plane, often installed behind stucco and in-front of plywood/OSB sheathing on exterior walls. However, such wraps must allow the structure to breathe (In hot-humid climates do not install wall-wraps that are vapor-barriers), or they will keep interior moisture from exiting the walls. They must also be installed so that moisture which penetrates the stucco or siding drains apart from the wall sheathing and away from the house.
(3) Vapor-retarders – Always let your interior walls “breathe”. Period. Make your ceiling as air-tight as possible (if your insulation is on your ceiling and your attic is vented). Period. Seal your slab. Period. The best way to allow moisture to leave the building is not to let it in, in the first place. Knowing that, whenever possible, exhaust your kitchen range to the outside (too often this option is not elected, and the range hood merely blows hot humid air and cooking pollutants back into the house). Bathroom exhaust fans should have timers or humidity sensors on them, and they should vent through the roof, or clear of the fascia. Too often, folks retrofit a bathroom fan by (a) running the hose into their attic – a very bad idea; (b) laying the hose on their soffit – this is the air intake of a vented attic (what are people thinking?); or (c ) add a through soffit exhaust (but, again, the dynamics of air movement just sucks the bath exhaust into the attic, unless the attic is unvented and sealed). If you’re not going to install a bathroom fan properly, don’t put one in, and just open the window when your bathing.
(4) In-floor radiant heat – most slab floors in Florida are un-insulated, and, in fact, act as a thermal mass for heating/cooling purposes. If you are going to heat your floors in this manner for the few weeks in a year you need heating, unless your heat source is relatively free (i.e., solar or geo-thermal) your money is better spent on other means of heating/cooling. However, if you are temperature sensitive (and there are medical conditions which make a cold floor extremely uncomfortable and painful to be in contact with), radiant floor heating is a great means of making your home comfortable. But, try insulating it first.
(5) The advice offered here is applicable to colder climates and places with basements. However, leaks are best dealt with by sealing with foam (if you can). Exterior places on a home where materials change, or walls change angles, will need to have their caulking maintained. Environmental conditions will lead to a deterioration of the caulking at window frames, soffits and flashed points where roofs and walls meet. As the caulk fails, hot humid air will leak into the house (when your AC is not running) and cold air will leak out (when the AC is running). Rain will be driven into these spaces as the cracks increase in size (due to lack of maintenance). You would be surprised to learn just how much water can enter a house through the many point penetrations and small cracks that are often left unrepaired by busy homeowners. Storm winds drive water great distances. So walk your homes, and repair these cracks as you find them.
(6) Energy ratings – Buyer beware. Know what you are buying. The best way to determine the energy efficiency of your home is to have an audit or test performed by a certified energy rater (the Florida Solar Energy Center maintains a database of certified raters in the state of Florida). Sometimes these audits and tests can be performed free through your power utility. Enquire about their programs to find out what is available to you.
(7) Foams – there are many different foams available (bio-foams, petroleum foams, closed foams, open foams, fire foams, etc …). They are designed for specific purposes and applied in a certain way to meet performance specifications. If you don’t know which foam to use (or use foam at all) for a specific application, ask a trusted expert.
(8) R-values. I can only echo agreement here – R-values are useless if the product is installed poorly, or installed in a poorly built assembly, or used in the wrong application.
(9) Remember: “Its the energy, Stupid” Joseph Lstiburek, P.Eng.