Author Topic: Do we need soffit vents before insulation is blown into our attic?  (Read 4509 times)

SomedayStache

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Yes - this is almost a dead horse and there have been multiple threads on insulation and attic venting.  I've read them.  I still have questions and I suddenly have a tight deadline because our electric company is subsidizing the cost of insulating our attic and we have less than 2 weeks before their appointment.

We have a 1700 sq ft ranch style house.  It has a ridge vent running along the length of the roof, a gable vent at each end, and one of those twirly things stuck randomly in the middle of the roof.

Everything I've researched says that we should have soffit vents in conjunction with the ridge vent to draw air through the attic.  Currently all our ventilation is near the top. There are no soffit vents.

Do I need soffit vents?  (The energy auditor guy seemed dismissive of the idea and told me he wouldn't put more holes in the house...but he's an energy auditor and not an attic ventilation expert).

If we need soffit vents, should we install baffles inside our attic to block insulation from overhanging the eaves when the crew comes to blow in insulation?  Should we try to install the soffit vents themselves in the next 10 days or can we wait on this part?

BudgetSlasher

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Re: Do we need soffit vents before insulation is blown into our attic?
« Reply #1 on: July 21, 2016, 04:11:12 PM »
I'm not certain if you need soffit vents (but everything I have read on that front says for a ridge vent to be functional there needs to be a lower inlet for air); you could go read up on http://buildingscience.com/ (they have great articles on just about everything). But, if you need soffit vents then you will need baffles to prevent the airflow from being blocked by insulation.

I don't consider a soffit vent putting another whole in the house; after all in connects an uninsulated area (outside) with an uninsulated area (the attic above the insulation).


lthenderson

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Re: Do we need soffit vents before insulation is blown into our attic?
« Reply #2 on: July 22, 2016, 04:31:08 AM »
Not sure where you live but in my area, I would most definitely have soffit vents in my house. The goal is to have your attic the same temperature as outside to prevent condensation. I'll guarantee without any soffit vents, your attic is always much warmer than the outside temperatures.

You do need baffles for blown in insulation and this can simply be a 2x6 or 8 depending on joists. As for soffit vents, these can easily be done after the insulation and from the ground outside without ever getting up into the attic.

Fishindude

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Re: Do we need soffit vents before insulation is blown into our attic?
« Reply #3 on: July 22, 2016, 05:19:56 AM »
You just need to do your best to get the heat out of the attic.   Soffit vents low and a ridge vent high are an ideal setup but not always practical.
I've got an old home set up much like yours.   When we moved in it had zero attic vents.   We now have gable end vents and ridge vents similar to your setup and it does OK.
I probably wouldn't add them.     

SomedayStache

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Re: Do we need soffit vents before insulation is blown into our attic?
« Reply #4 on: July 22, 2016, 07:09:35 AM »
Thanks all!  Current plan is to go buy baffles and an equal number of vents tonight.  We'll install the baffles before the insulation crew arrives.  It would be nice to install the vents as well and be done, but if we don't have time for that we'll do it later.

The tricky part is going to be somehow notating where the baffles were installed so we put the vents in the right place later.  I guess we should really try to do the vents first, then add the baffles where needed.  I hate being on a time crunch for these things!

Drifterrider

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Re: Do we need soffit vents before insulation is blown into our attic?
« Reply #5 on: July 26, 2016, 06:11:45 AM »
The cooler the attic, the longer your shingles will last.  Optimally you will have a ridge vent and your soffits will be totally vented.  More soffits vents is better.

Of what material are your soffits currently made? 

Frugal Lizard

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Re: Do we need soffit vents before insulation is blown into our attic?
« Reply #6 on: July 29, 2016, 12:44:51 PM »
Last year we got soffit vents installed and baffles and then re-insulated the attic.  We are in a cold climate and only had about R15-R20 in the attic.  We got the existing insulation removed so that we could check the wiring after a substantial mouse infestation in the attic.  The electrical in this house has been dicey and when we got the feedback about the lack of insulation, the mice and put it together with what we knew about the wiring in the rest of the house, we decided to clear out the existing insulation.  We had significant problems with icicles on the roof (enough that kids weren't permitted near the back of the house) Eaves troughs (gutters) were also not working well and had sagged so we had issues with water in the basement.
We consulted a couple of builders and two architects as well as the insulation companies. 
No one felt that the roof vents and gable vents were sufficient. 
In hindsight it would have been easier to have the insulation blown in while the soffits were off and had the baffles installed at the same time.  Our roof is very low sloped so two of the insulation companies wouldn't even bid the job.
No icicles at all this past winter.  I think the weight of the icicles was really hard on the gutters so this was good to get resolved.  We didn't just cut holes in the plywood soffit - they were completely removed, including on the gable ends.
We did discover that the mice had not chewed any wires and that there was none of the weekend warrior wiring that was in the rest of the house. It was a fairly expensive bill for piece of mind.  But now we don't have to worry about wiring, mold, a child getting impaled by an 8 foot icicle and our house is definitely warmer in the winter and cooler in the summer.