Attic venting
darwyn
| Posted in General Questions on
Should an attic be vented in a 90+ year old, two story cottage? It had minor insulation in the attic and I have to believe it isn’t air sealed. This building was a summer fishing lodge in northern Michigan for many of its early years.
We are having a steel roof put on and the roofer suggests putting a power vent on the north side of the roof to keep the second floor cooler on warm summer days.
Currently the only ventilation in the attic is from one gable end vent.
Does this sound like a good suggestion?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Hi Darwyn, this aritcle from Energy Vanguard looks into attic temperature in detail and the article start by asking whether power venting is optimal or even necessary. It lists reason why you may want to keep the attic cooler, and why it may not be necessary. The article is well written and I would not try to repeat what is contained in the article. Here is the link.
https://www.energyvanguard.com/blog/the-best-way-to-cool-your-attic/
Choosing a light colour for your metal roof is going to make a big difference. You could even choose a reflective finish like galvanized or galvalume. Here is a page that compares both products.
https://sheffieldmetals.com/learning-center/galvalume-vs-galvanized-metal/
I noticed in the article (first link) they mention a less formal study using reflective materials and the non-scientific results were described as follows:
"My experience with my own reflective roof is going on three years, now. Each summer has been consistent with air temperatures in attic tracking below outdoor ambient until mid afternoon, where it then tracks with outdoor ambient."
Hoping this is helpful.
Thank you for your input. Since this cottage is not air conditioned and most of the owners like to keep the windows closed to keep the space cooler, the vent will be pulling in air from every crack and crevice in the house.
darwyn,
If the cottage shows no signs of moisture problems, and all you are doing is re-roofing, you are best to not change anything which may upset the present equilibrium. If you start adding insulation, then you need to choose a roof assembly which will either be vented or not based on the materials used.
Thank you Malcom. I appreciate your help with this question.
I agree with Malcom if you are content with the status quo change as little as possible.
If this is a story and a half building you struggle to heat and the roof sheeting is coming off now might be your only chance to air seal this energy pig. I hate spray foam but the house I just described is one I say spray foam it.
Walta