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Install louvered vent with flashing behind hardie plank

Install louvered vent with flashing behind hardie plank

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  #1  
Old 05-09-15, 12:40 AM
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Install louvered vent with flashing behind hardie plank

I need to install a louvered vent VP528 into side of my house. The vent includes a square box protruding into wall where I can insert 8" round pipe (to vent-a-hood). It also has 1.5" surround flashing that installs against sheeting under the siding. Here are pictures:

http://ventahoodparts.weebly.com/upl...47697_orig.jpg
http://s1.img-b.com/ventingdirect.co...es/VP538-2.jpg

What is best way to cut square into hardie plank siding and how do I get surround flashing installed under it? Any special steps to caulk or weather proof this?

I would like to make this as clean and unobtrusive as possible (very visible area of house for a very large vent).
 
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  #2  
Old 05-09-15, 01:16 AM
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Your description sounds like that box gets installed before the siding goes on. I'll let the better contractors advise if and how you can install what you have.

Just a frequent comment I always add when someone is installing a large exhaust hood, that 8" duct you mentioned, but high volume exhaust hoods can depressurize a house enough to backdraft some combustion appliances, like naturally drafted hot water heaters and furnaces. If it is rated at over 400cfm it should have had instructions about necessary make-up air. More details if needed.

Bud
 
  #3  
Old 05-09-15, 05:14 AM
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The right way would be remove the siding, install the vent then reinstall the siding cutting it to fit around the vent.
The siding can be removed by cutting the nails with off with a long bimetal sawsall blade slipped under the sidiing.
 
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Old 05-09-15, 07:06 AM
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If you can't remove the siding as mentioned above, or don't want to for some unknown reason, you would use a grinder and diamond blade to cut out the square. But you would need to cut a square that is big enough for the vent AND the flashing AND some trim.

So let's say the vent is 12x12, and you will be putting a cement 1x4 around that as trim (to cover up the nail flange. The 1x4 on each side adds 7"... so you would cut a hole thats slightly over 19x19. You would then install a z-flashing (drip cap) under the siding on top, install the vent, cover the fins with some window and door flashing tape... getting it as far behind the siding as you can (peel and stick) then install the trim over that. Bottom piece of trim 12" long, top piece 19" long, side pieces 15 1/2" long. Caulk all joints when assembling it.

Doing it this way will make the vent look larger and even more obvious, which is why removing the siding and installing it up tight to the vent is the preferred way to go.
 
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Old 05-09-15, 10:59 AM
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Thanks for help - hear are my plans

The square hole protruding into house is same as the size of the square hole for the siding. I am going to use a skill saw with diamond blade to cut this out while siding is still on house (with mask and a shop vac trying to pull away all the dust). I will then chisel out and remove the surrounding siding (trying to cut out nails from underneath using a hacksaw blade).

I will install vent after adding some Vulkem sealant between it and sheeting / water barrier. I will use flashing tape over the vent edges. I will then reinstall the hardie plank siding (hold up in place with some 2x4 and pre-drill new guide holes since I can't do hidden nailing). Once done I'll spray in gap filler from other side of wall and install the 8" pipe wrapped in insulation. Wish me luck and any advice is still welcome.
 
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Old 05-09-15, 01:50 PM
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If you are using a skilsaw, an actual fiber cement blade (4 or 6 tooth carbide) would probably work better than a diamond blade.

I guess now that I look at the vent (never looked at your link before) I would cut out the hole in the siding a bit bigger than your overall vent dimension... but try not to cut the sheathing. Remove the siding cutout (which will be roughly 12x12) then cut the 8x8 hole in the sheathing for the box... then apply the flashing tape to the sheathing to protect any cuts you made in the housewrap and sheathing then trim the edge with 5/4x2 then put the vent on top of that trim.

Also you mike want a take off adapter, kind of like this one: http://www.homedepot.com/catalog/pro...2f37e9_300.jpg

Bend the tabs into your box where possible, seal perimeter with foil tape.
 
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Old 05-10-15, 09:40 PM
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XSleeper - Thanks for the great advice! I was able to put the vent in yesterday with a slight modification (I put trim on outside of vent flashing). Here are more details for anyone that may come across the thread..

1. From inside of house I used drill to mark the center and measure. I used a skill saw (carbide blade was best I had) for cutting the hardie plank, and a sawsall to finish the rest of the interior cut. This first cut was for the interior dimension of the vent that would go into the house. This gave me practice on cutting hardie plank for the more visible cuts later.

NOTE: Next time I would have wrapped a piece of metal around an ABS vent pipe that was in the wall near my new opening (sawsall put small nick, but plumber is already coming for other reasons and he can fix).

2. I then measured width for the outside of the vent flange plus just a bit more so the siding had room to expand/contract. I set depth on skill saw blade to avoid cutting through to water proof barrier. But no luck - plastic had draped out against the lap in the siding. Next time I might try to slide a sheet metal to protect the plastic sheeting when I was cutting the outer cut (or don't go as deep and spend more time with a chisel).

3. I fixed a new plastic sheet water barrier where I had cut through.

4. I used a knife/chisel to cleanup the cuts from the skill saw and carefully broke the hardie plank to make a nice clean edge. The hardie plank did eat the carbide skill saw blade, a couple utility knife blades, and take off the edge of old chisel.

5. I put very generous caulking on back side of vent and screwed it up onto the plywood sheeting (sealed against the water barrier).

6. I then installed the cedar trim with more caulking on the outside of the vent flashing. I predrilled the holes and sank the screws deep enough to cover with caulking.

NOTE: The trim was 3/4" thick. I underestimated how much lap siding protrudes. I may go back and install 1" thick trim instead. Adding this trim over the flashing of vent-a-hood VP528 helps make it appear less obtrusive (but be careful not to block the louvered flap on bottom).

7. I put caulking between the hardie plank and the new trim so that water coming down the siding should go over and around the vent. If not, the flashing of the vent should be another barrier. If not, plastic water barrier should be a third.

Thanks again for all the help!

Bud9051 - The vent-a-hood BH234SLD has two fans with variable speed allowing "upto" 600CFM. We will only use full rate for short durations of special needs (and in those cases we would likely open windows to get rid of that smokey air :-). When you redo kitchen the chef gets to pick the hood. I'm sure it will make steaks taste that much better :-).
 
  #8  
Old 05-11-15, 02:33 AM
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The old "good intentions" and "open a window" solutions fall way short of code and safety if you have naturally drafted appliances. I just want to be sure you understand that with a 600 cfm exhaust capability you may be required to have a powered make-up air system in place.

Even if your codes do not require it, if you have those appliances, even a short run at high speed could be pulling all of the combustion exhaust back into the house.

Bud
 
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