I’ll start by saying we Mississippians should add another rule to the 3 rules for venting attics. Call it a bonus rule for Mississippi.
- Bonus Rule: You need a minimum of R38 insulation in the attic.
However – because this state does such a poor job of managing energy efficiency standards you should consider yourself lucky to have at least R30. R-value is a measure of how well your wall or ceiling resists the conductive flow of heat. A higher number is better. Most older homes in Mississippi have compacted loose-fill fiberglass insulation with R-Values less than R30 and even “new construction” is typically installed at “only R30”. New construction should be R38 – but our code officials don’t enforce installing more insulation. If you are building, discuss this topic with the builder.
The 3 rules are:
- Start with insulating a sealed ceiling plane. TOTALLY SEALED – No Christmas tree storage, nothing in the attic, nothing but air and insulation. Put the attic access hatch outside the heated and cooled area (in the garage or porch ceiling). Put your extra stuff in the storage room!
- The entire perimeter of the roof needs to have air inlets, meaning continuous soffit ventilation. Wash the underside of the roof decking with air.
- No whirligig turbine vents or power vents — they depressurize the attic, and if your attic ceiling isn’t perfectly airtight, they’ll suck air conditioned air or heated air out of the house.
WATCH THIS VIDEO by Dr Joesph Lstiburek.