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When we moved into the house we live in there was literally no insulation in the attic. We have a 4 1/2 pitch roof. We live in Texas and our first electric bill in a 1450sf house was almost $500. Of course, this sent us reeling. The only attic ventilation is through gable vents. A friend blew in 3' deep insulation. Our electric bill dropped over $300 the next month to about $150. Now, due to hail season we are going to replace the roof. I have had as many ideas on how to best accomplish attic ventilation as I have had contract proposals from roofers. I understand the best way to ventilate is with soffit vents all around the house. I have a problem with this. The pitch of the roof together with the depth of the insulation make any attic access from the inside impossible. The depth of the insulation comes to the bottom of the gable vents. The soffits are closed. I hate turbine vents. I am looking for a balance of cost effectiveness and the best way to accomplish correct ventilation.

Given the small cubic footage of attic air, is it more feasible to install a ridge vent (roofline is about 45' long with two 15' ridges in the front of the house ... gable vents only on the 2 ends of the house) or power vent(s) since there is not much airflow moving upward naturally. Also, is it possible to install soffit baffles from the outside of the house? As I said, it is impossible to access the attic to staple the edges. The decking is shiplapped planks not plywood. Would it be possible (and not too much trouble) during the tear-off of the roof to temporarily remove planking and install the baffles by reaching through the openings from the outside, or does anyone have a suggestion on how to poke some kind of baffle up through a hole in the soffit from the outside (maybe something like pcv pipe or something similar? I have been told that without some kind of power ventilation in the center of the ridgeline or soffit baffles there will be stagnant air in the center of the house and the overall ventilation will not work properly.

Today the outside temperature was about 90°F and the attic temperature was about 150°F.

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Have you asked your roofing contractor for advice? They probably deal with this kind of thing all the time. –  longneck Jun 10 '13 at 15:25
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1 Answer

Are you planning on replacing the roof? If so, are you redecking the roof or just replacing shingles? If you're only replacing shingles then there will be little or no additional opportunity to install soffit vents. If you are redecking, make sure to use radiant barrier decking. It adds about $2 a sheet to cost and has a large impact on attic heat. No roofer will tear off and reinstall old decking.

Soffit vents vs gable vents vs whirlybirds vs vent fans will make little difference in attic temperature in Texas. I have had houses with all combinations, and no vents at all, and the effectiveness is as follows:

  • Soffit vents (almost no effect)
  • Gable vents (little effect)
  • Attic fan with gable vents (some effect, still easily 140+ in summer)
  • Turbine vents with soffit and/or gable vents

I made the mistake of replacing turbines with attic fans on one house and the temp in the attic went up!

You can definitely hire someone to install soffit vent channels, and they will come rake all of the insulation out of the way and install the channels, then move the insulation back. The impact of soffit vents will be minor though.

Honestly, if you are are not having moisture issues in your attic (i.e. you don't live in Houston) and you have a house built before 1970 in Texas with a $150 summer electric bill then you probably want to stop worrying about the attic and start looking at other systems for improvement. If you had no attic insulation then you probably have no wall insulation. Having insulation blown into the walls will have a noticeable effect. Have you replaced the windows with low-e vinyls, esp. on the south and west walls? That will also have an impact on cooling costs. After all of those, start looking at A/C upgrades, pressure testing (most utilities will do this for free or low cost). Soffit vent channels and retrofit radiant barrier will have negligible effect if you already have several ft of insulation in the attic.

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