High humidity in spray foam attic
Last fall I had my attic spray foamed. Warm temperatures have arrived and I am experiencing higher than anticipated temperatures and humidity in my attic.
I have 3 main questions (pertinent details follow):
1. Is a semi-conditioned attic RH in the 60 – 70% range cause for concern?
2. Should my attic be 10+ degrees warmer than the interior? It will get much warmer here in the coming months and I am worried that the attic temperature difference will grow.
3. Is the fact that the ridge vent is still in place (but foamed closed) a possible source of high humidity in the attic?
Here is what I recorded yesterday in late afternoon:
Attic: 86F / 71% RH
Outside: 88F / 44% RH
Inside: 76F / 50% RH
And this morning at 9AM:
Attic: 74F / 53 % RH
Outside: 74F / 75 % RH
Inside: 76F / 53 % RH
Here are my home’s details:
– 1960s ranch approx 1400 sq ft
– Climate zone 2
– Dark roof shingles with a sealed roof deck
– 5.5 inches of open-cell Icynene which covers the rafters
– Roof was previously vented with a gable vent and ridge vent; gable vent hole was sealed and foamed and ridge vent was foamed
– Crawl space has been encapsulated / sealed to exterior and has a SaniDry CX dehumidifier set to 50% RH
– New 2-stage heat pump (American Standard / Trane) sized correctly with dehumidification function set at 50%
– Blower closet (central return) was sealed off from attic with spray foam
– Ductwork is in attic; no supplies or returns have been added to attic
– Original rigid ductwork has not been mastic sealed and has original paper-backed fiberglass insulation covering, some in poor condition
– No plants, aquariums, or other additional humidifying sources in home
– New range hood vented to exterior through roof
– New bathroom fan with humidity sensor vented correctly through gable end
Thanks for your consideration!