Blow-in insulation - recommendations?

[treeguy]

We are in the market for a vendor to insulate our attic before winter.  Anyone have any recomendations?  Thanks.

[T-Stan RPCV]

I think I might be stating the obvious but some roofers still don't get it;

Whoever you choose do not allow them to block soffit vents (if you have them) with blown in insulation.  This will cause the roof sheathing to rot and be destroyed in a few years.  I've seen this over and over again and you'd think roofers would have figured it out by now, many have not.

[Ana]

Okay, you have me worried.  I don't have soffit vents, at least not where I can see them.  We have the original beadboard soffit, not vents.  Should I worry?  We also had our roof replaced about 4 years ago.

[Ted]

  What is a "soffit" vent" ?  And, what is a "beadboard soffit"?

  Thanks
    Ted

[Bonster]

the soffit is that foot or two of wood or other material extending from the house to the edge of the roof (gutter).  Newer installations will have vents in them to allow airflow in certain pockets of your attic.

Older homes with the nice wood soffits (beadboard, a nicely grooved/shaped wood) did not have them, and without tight seals at the attic entrance, are prone to problems with humidity, such as winter frosting.

[Robert Pauly]

Now I'm getting confused.  Isn't airflow in an attic desirable (to prevent excess humidity, condensation and rot)?  Don't the soffit vents and the vents at the peak of the roof work in tandem to provide attic airflow?

[Bonster]

yes, airflow is desirable. 
By tight seal I was referring to the entrance from your second level, provided your attic is not a climate controlled living space.  Gaps at the bottom of the door, etc. will allow humidified air up there, and without good ventilation you'll encounter trouble with frosting in the winter.

The designs of many older homes did not include soffit vents, and the finished attic flooring went to the edges of the attic anyway (not allowing air flow up from the soffits.

As long as your ventilation is sufficient you'll be ok. 
I presently have two small roof vents.  I'm considering a couple of additional vents, along with a fan powered vent.

[T-Stan RPCV]

Perhaps I should not have opened this can of worms.  We are going through a home purchase where the seller blocked the vents and the entire roof (<10 years old) is shot.  It might be a deal breaker.  I sometimes inspect homes and was ironically pissed off when I found a condition I've seen in so many other homes afflicting a home I really want to buy.

Bungalows are mostly designed with a cold roof deck.  During winter months the air at the interior surface of the wood roof deck should have approximately the same temperature and relative humidity level as outdoors.

To prevent problems two things must be accomplished:
- The roof deck should be cold so snow melts from the top not the bottom.  Snow melting from the bottom will re-freeze at the eaves causing ice dams and water to back up under the shingles and into wall cavities.
- Humidity from the home must be exhausted to prevent condensation from forming on the cold roof deck.

Traditionally this was achieved by gable vents at either side of the attic to allow outside air to flow in and out and perhaps a few mushroom vents to allow air to exhaust.

Most updated homes will have vents under the soffit and a continuous ridge vent along the top of the roof or mushroom vents.  This allows outdoor air to enter at soffits and flow up through the top to better distribute the outdoor air over a larger surface area.

If you have a traditional gable vent system you should be OK.  If you have the soffit vent system then blocking the soffit vents provides no outside air intake.  The pressure created from wind traveling across the ridge vent (or a mechanical exhaust fan) will pull the higher relative humidity air from the home into the attic where it will condense on the cold roof deck and cause problems.

In our desire to constantly update our homes with the latest and greatest many bungalows have had the soffit vents installed.  The need to reduce energy costs in our drafty homes then results in blowing in insulation that obstruct the vents and in a few years its time for a new roof.

[Bonster]

no worms, T-Stan, just good info!  Gable vents are just what I need!

-  If you have nice beadboard soffits, I wouldn't vent them; I'd use alternative means for ventilation.
- With respect to powered vents, the surface area for intake must be great enough that air isn't pulled from the conditioned space
and

- Any openings/entrances to attics must be sealed just as well as any door or window leading directly outside!

Our door to the attic had about a one inch gap at the bottom, and was not sealed at all whatsoever.  Also, our bathroom fan, although vented outside, wasn't sealed at that point, blowing nice, humid bathroom air into the attic.  Although we haven't had ice dams, we have had frost on the interior surface of the wood deck.

[treeguy]

Hey Guys,

Great discussion on soffets.  Anyone have any recomendations for a roofer or insulation service?  Thanks.

[Ana]

We had our roof replaced by Suburban 6536 Cermak (Joe Cimaglia).  They did a very good job.  We received lots of compliments.  Price was decent.  He met a lower price that we had been quoted previously.