Cool in June

Posted on 17. Jun, 2014 by in Architecture, Building Science, Caring for your Home, Eco-Inspector, Energy, Healthy Home, Heating and Air-Conditioning, Nature

The Streetlight Effect: convenience trumps reality

Thermostat Wars and The Streetlight Effect

Too much A/C gives me sinusitis, too little and I can’t sleep.  You may be comfortable at 79, but it’s 78 for me. Family beach week is a constant battle between the 70F-crew and grumpy uncle Dan.
Individual comfort depends very much on the specific needs of the comforted. How homeowners solve cooling deficiencies depends upon their understanding of the problem. When I see a fan in every room during an inspection I consider the Streetlight Effect.

The Streetlight Effect 

The easy fix is tempting.  The quite human tendency to accept the most convenient solution is known as The Streetlight Effect
http://io9.com/5983112/how-the-streetlight-effect-keeps-scientists-in-the-dark

Ceiling fans (Air velocity) is just one of six comfort metrics. 
http://www.hse.gov.uk/temperature/thermal/factors.htm

Common Cooling Fixes: 

More fans may be a simple answer but not the right solution

Appliances:  Rule of thumb load calculations and latent discomfort

Rule of Thumb vs Load Calcs
Determining appliance size and duct layout with default measurements from what was done on the previous job is a Streetlight Effect shortcut.  Make your HVAC installer perform appliance and duct load calculations to determine the correct amount of energy it takes to heat and cool.  Too big, small, fast or slow may compromise comfort. Software makes the math easy.  Meet the Code, do load calcs 

Over-Loads: 500 square foot vaulted west-facing addition with 12 windows and 3 skylights

 

It’s not the heat, it’s the humidity  Latent heat control is the key to comfort.  Opt for dehumidifiers and variable speed appliances. Unmanaged humidity is conducive to mold.
http://www.buildingscience.com/documents/bareports/ba-0214-conditioning-air-in-the-humid-south-creating-comfort-and-controlling-cost

Building Enclosure:  Don’t let living large=costly discomfort

Fouled filters are the HVAC equivalent of going for run with sock stuffed down your throat

 

Big homes don’t have to be energy-expensive and uncomfortable.  Atlanta has a corps of energy-savvy design and installation experts trained to fix problems like:

  • Energy-hogging FROGS (family room over garage)
  • Hot-topped, cold-bottomed split level homes
  • Vaulted, glass-walled, skylit BIG ADDITIONS 
  • Burning Hot Poptop attic conversions

Atlanta’s Southface http://www.southface.org/ is a clearing house for energy efficient, healthy design

Use industry standards for comfort and health

Don’t monkey around with Ducts

Obsess about furnace filters.  Dirty filters are bad for airflow, equipment, and air quality
Balance airflow with larger, strategically located return air openings
Support and straighten ducts. Crushed and sagging ducts slow airflow and dehumidification. 

Holes in pressurized duct systems blow your dollars away.   Secure and seal ducts and plenums
Take it inside  Ducts and equipment in 150F Hotlanta attics are 45% less efficient than those in conditioned space

Cooling comfort is attainable and sustainable.  Contact a comfort-smart independent inspector who knows his BS……before you buy that next fan.

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