Replies

1. 
   Piffin | Mar 12, 2005 07:08am | #1

   It sounds like you have contradictory systems with roof vent and whole house fan. I am guessing that you are located in the south because of that big fan.

   Since my understanding of venting is for northern heating climates, I won't comment but to direct you to buildingscience.com
   I don't think there is anybody with abetter understanding than Joe Lisiturbrck

    

    

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   Taunton University of Knowledge FHB Campus at Breaktime.
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1. 
   prosecho | Mar 14, 2005 12:37am | #3

   Thanks for your imput,I have been reading some stuff at buildingscience as sugested,deep stuff .
   The house is Nebraska .Near Lincoln. This house has no vent but the coupola over the garage Cedar shingles ,over 1x12's no spacing .It does not appear there were any problems in 40 years .The shingles are pretty soft and brittle ,only failure in roof system appears to be in the flasing around chimney and some of the vents.The insurance company said they will replace the shingles with heritage .As the fire only damaged a small section of the roof.The home owner was happy about that as he was planning on redoing his roof this comming spring.Is this venting stuff really an issue?I remember back east in Boston area replacing rotten roof sheeting on one whole side of the roof cause the sheeting was so rotten .This is not te case here .Still searching .Thanks
   Rick

2. 
   IronHelix | Mar 12, 2005 03:00pm | #2

   You have two "systems" operating.

   First is a passive ventilating system for the roof system, which needs soffit vents at the perimeter of the house eaves and then another set of vents set closer to the ridge.

   Could be hat, turbine, ridge, cupola or power vents.  The total "free flow" area of the upper vents should meet your locally sized needs....see Piffins posted reference to EEBA.

   The amount of free flow area of the soffit eave vents should be equal or greater than the calculated exit vents on the upper portion of the roof.  This paired set of vents then allows for the cooler air to enter at eave level and rise as it warms to sweep the heat/moisture out of attic space to then exit at the top vents.

   The second system is the whole house fan that is designed to suck air into the living area by blowing air out of the house throught the attic.

   This system also has a balance point. The manufacturer of the fan, by model number, has a set of specifications for the number of cubic feet of air per minute your fan moves.  And has a minimum recomended number of "free flow" square feet of vent area for exits to give that fan adequate air flow to function properly.  Check it out at the manufacturers web site, or by comparing the current fan to an equal one on the shelf at your local supplier.

   I have my doubts that a 3x3 cupola has enough "free flow" area in its ventilation louvers to handle the whole house fan exhaust.   Once again "free flow numbers are available for calculations.

   I recently installed a 36" attic whole house fan that specified 16 square feet of free flow exit. As a result of those requirements two large gable end ventilators were constructed.   Search in the picture gallery for "attic louvers" & Iron Helix.

   Most houses i inspect that have a whole house fan installed are not properly sized for the exit vent size and prevent the WHF from doing its job.  In some cases there are no vents.

   When the WHF is running the passive attic eave/ridge ventilation system is also an exit area for the forced air into the attic.  The manufacturer of the passive vent system materials has those free flow statistics to help you calculate and balance the attic air flows.

   You will also have to protect the cellulose from being blown around by the volume of the WHF's draft.  Build a box to extend the sides of the fan upward and/or apply fiberglass screen on top of the celulose in the area around the fan to prevent blowing cellulose.

   If the wood shingles lasted forty years...I would assume they are installed on spaced 1x nailers.  Be sure to go back with the same to get another 40 years.

   The wood shingles offer a design challange...as most of the passive ventilation products are designed for asphalt shingles.

   Good Luck............Iron Helix

    

   PS...My house also has a WHF, love it. Come to think of it...so did my grandather, dad, uncle, cousin, two business buildings....and on& on!

1. 
   prosecho | Mar 14, 2005 12:50am | #4

   thanks for your post The shingles are on 1x no spacing
   My gut instinct was the coupola was not big enough to handle the whf
   no gable vent ,no roof vents,no soffit vents
   No problems?
   Will it really change much if I go from wood to asphalt.
   I could try convincing the home owner he needs to do something but I am not convinced myself,yet.Please see last post to piffin

1. 
   IronHelix | Mar 14, 2005 04:04am | #5

   Hey...where is this house located....what region of the country? May change what needs to be said & done.   Usually part of your profile when you sign on BT.

   A forty year old house was built "looser" than the current houses and therefore breath away the moisture generated by habitating in a house.  Likewise the 1x sheathing breathes a whole bunch more than roof panels...hence the 40 year duration.

   If it isn't broken don't fix it!   Unless the changes you make to the house will change it's environmental configuration...then you may have to address preventative measures, or adapt current best methods of building.

   Asphalt is a tighter membrane on the roof sheathing, thus it will hold moisture and heat in the attic better than looser fitting wood shingles. 

   Likewise the asphalt shingles have more thermal mass and will hold more of the winter nights coldness for the humidity leaking from the warm moist house envelope into the attic to be condensed on the bottom side of the 1x's that are well cooled by the asphalt shingles.

   A closed attic will generate a lot of heat that will effect the potentail life span of the asphalt shingle and drive the cost of A/C operation up and often overburden a compressor, shortening it's lifespan.

   Wood is more expensive and labor intensive.  But the $$ for retofit ventilation might drive the two choices to similar totals.  Do the numbers.

   Will the change effect the "look" of the house design and setting?  Will the owners mind the visual change?

   You need to adequately vent for the WHF for proper results. Adding vents/louvers is not that big a deal.

   ..................Iron Helix

2. 
   IronHelix | Mar 14, 2005 04:24am | #6

   Just read your post to Piffin and downloed the pics. 

   Those wood shingles look really in poor shape!  Wow!

   Changing to Heritage Architecturals will definitely change the look away from the "woodsy rustic cabin" feeling...but it might be okay if it would please the owners.

   I'm a "woodsy" type of designer/builder and would vote for the wood shingle roof to keep "that  look"...IMHO!

   Locally Fire retardent treated wood shingles range from $150-250 per square plus install...asphalt is going for about $45/sq plus install.....no wonder the insurance people are so eager to do the asphalt.

   An ideal place for a nice set of woden louvers is on the garage gable end.  Would look good and solve the WHF air flow problem.

   If this house in in a wildfire area, I would be doing some clearing back of the brush and undergrowth.

   Is that knob & tube wiring I see i the attic rafters?

   ..............Iron Helix

1. 
   rez | Mar 14, 2005 05:28am | #7

    

    

2. 
   prosecho | Mar 14, 2005 07:24am | #8

   The house is in Milford Ne,South west of lincoln out by the Great Plains
   The tree's you see here are not the norm though anything grows here.
   Had to laugh you noticed those wires ,not knob and tube .The guy (a banker )who had the house built in 1964 had antennae wire in almost every room ,TV and Radio I guess.
   I like the gable vent idea ,the coupola burnt off the roof ,fire ran up it.
   I am inclosing another view of the back side of the house ,notice the gable end ,that ridge run about 75' the other direction .roof is about 6300 sf.
   Soffits where plywood original,still below vinyl soffits instaled in 1994.no vents in either.I have to replace some of the soffit .The vinyl soffit replaced 10 years ago Alcoa woodland green ,color still available but old stuff was textured new isnt.Adding venting soffit is not difficult but ,I don't think the homeowner will want to spring for it unless convinced its absolutely needed.I am not,yet.
   Thanks
   Rick

1. 
   rez | Mar 14, 2005 07:41am | #9

   Greetings Rick,

   http://forums.taunton.com/tp-breaktime/messages?msg=24441.1

   is an old thread here on Breaktime that includes a lot of data on posting pics and the Irfanview download.

   Dialup patrons of the forum cannot download real large files or will take excessive time.

   Two things are necessary to assist the dialups with your photos. Making sure that the set file association is set to jpgs if you are using the Irfanview system.

   The other is to keep the KG picture size to preferably below 100KG 

   Some start downloading a pic only to go get a cup of coffee, heat it up, come back and find the file is only half done downloading.

   Cheers

    

2. 
   prosecho | Mar 14, 2005 04:54pm | #11

   My apologies
   Ive taken your advice and got the download irfanView
   I didn't understand why you posted the first timeThank You
   Rick Sheehan

3. 
   rez | Mar 14, 2005 05:14pm | #13

   Rick-

   One other help to better the pics in Irfanview is lightening dark photos to provide better clarity.

   After opening in Irfanview and setting the file associations, when you go to the 'image' column to Resize/Resample to around 640x480, look down to the 'Enhance Colors' and click there.

   In the left column you can slide the 'Gamma correction' tab to lighten the photos.

   cheers

   be no apologies necessary :o)

   Edited 3/14/2005 10:16 am ET by the razzman

4. 
   IronHelix | Mar 14, 2005 01:48pm | #10

   Nice ashlar stone veneer....good color combo. Well done modern 60's, worth preserving.

   Once again....I still lean strongly to the wood shakes, but understand if the $$$ difference commands the architectural shingles.

   Might check out some of the 40 year shingles for a little more visual definition. There used to be an asphalt shingle called a "Shangle" and was really thick butted at the edge.

   If you go with shingle, go ahead and add the shingle-over ridge vent to add some method of air exit if you do have to retrofit the soffits. 

   Be sure to add the proper roof vents into the asphalt shingles for bath fans, kitchen fans and any other venting appliances.  It was common practice in the 60's just to dump them into the attic....might keep another moisture problem at bay.

   One approach that could be taken, and would give the pocket book a break is to use the dimensional heavy asphalt shingle with the ridge vent and "Monitor" for water/condensation problems for the next year on a quarterly basis.  If it arises then address it, if not then your changes are okay for the house.

   When you do the cellulose, add the soffit baffles before blowing.  I assume you are keeping the WHF......I would, extend the WHF chase, cover the cellulose around the WHF opening with  staple down 48" wide fiberglass sreen wire and then add the correctly sized GE louver and drop the cupola. Then, loosing the cupola would not be a big deal visually and vent wise.

   Add an elevated service runway out of plywood the length of the attic run for your return service work.

   Also before blowing....Mark the location of all the electrical junction boxes and other service related items on the rafters or decking above...plumb bob does an excellent job. 

    

   ....................Iron Helix

    

   PS....thanks Razzman, that was much less load time!

   Edited 3/14/2005 7:03 am ET by Iron Helix

5. 
   prosecho | Mar 14, 2005 04:56pm | #12

   Thanks Great stuff ,I can tell you really have a feel for what I am dealing with.Thanks For looking