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yayoubetcha
New Member
Posts:13
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| 08 Apr 2013 02:00 AM |
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Regarding the vent clearances for the DV fireplace,
No offense to all of the contributors but take all of the advice given and toss it in the lake behind the house. Some was good but much of it was false and misleading. I have sold and installed a few (1000+) fireplaces that burn wood, natural gas, propane, pellets, coal, corn, alcohol, you name it and the only documentation that is looked at is the fireplace and venting manufactures installation instructions. Each fireplace will have a LISTED venting supplier in the manual. You are only approved to use those suppliers. That is how they are certified and listed.
I have never met a building inspector that had a clue about fireplaces so they would never pick that up. The only thing they usually check is combustable mantel clearance and the air test on the piping. They care about one thing and one thing only. Permit fees. I have seen many homeowners and unskilled carpenters try and burn down a perfectly good house by doing a crappy job on a stove or fireplace and the so called inspector bought off on the job due to ignorance of the product being inspected. I am not saying all BI's are like this, just the ones I have dealt with.
Most venting manufactures require the use of a wall thimble that provide proper clearance to combustables however I have never seen one that is specifically made for the depth of an ICF wall. I have made a few custom thimbles for this exact reason. Some horizontal caps have a built in thimble and are not easily modified nor should they be. Also, some specific fireplace models are listed with a brand specific, insulated wall thimble that must be used on that install. I missed this once on an estimate and it cost me $100 when I installed it and only charged for a standard thimble.
I don't want to insult my fellow posters but be very careful when playing with fire and be even more careful when taking counsel on it.
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“The enemy of a good plan is the dream of a perfect plan.”
― Carl von Clausewitz |
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yayoubetcha
New Member
Posts:13
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| 08 Apr 2013 02:23 AM |
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The flue gas temps are not 400º. These are "reasonably" efficient fireplaces. The gas is burnt in the bottom of the box. The box acts as the primary heat exchanger which will drop the temps considerably. That is where the convection heat from the fireplace comes from.
There is no "space" between the in and the out.The pipes will not be aluminum.
Prior to the gas valve opening, the flue fan must prove air flow. It is not convection. Okay...I don't want to offend you but I have no idea what you are talking about. For direct vent gas pipe they generally have 2 sizes, 4" x 6 5/8" or 5" x 8". The inner is smaller and there is an airspace between them. The inner is usually aluminum and the outer is galvanized on the pipes but some decorative caps are stainless, copper or all aluminum. The only thing the gas valve needs to open is proof of fire from the thermocouple and power from the thermopile or on a newer electronic ignition unit a signal from the flame sensor and power from the batteries or 120v line. I have only seen a vacuum switch in pellet stoves and the Mantis line of gas stoves. All others rely on convection for draft and proper flame pattern and appearance. Again, I don't want to throw mud but your post makes no sense to me. |
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“The enemy of a good plan is the dream of a perfect plan.”
― Carl von Clausewitz |
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Lbear
Veteran Member
Posts:2740
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| 08 Apr 2013 03:15 AM |
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 The above is my gas direct vent FP flue. As the above person mentioned, there is an airgap space between the exhaust gases and intake air (see photo) and the pipe is made out of aluminum.  Another mentionable is that these direct vent FP flues are notorious for letting in critters into the home. Out here in Arizona (scorpion & bug country), these flues are basically open to the outside and everything that can crawl through that wide spaced wire cover will find its way inside your home. I have to place sticky glue traps inside the fireplace base in order to catch the bugs. Even then they don't all get caught and we eventually get bugs inside the home. The exterminator recommended taping shut the flue during off season. Of course turning the pilot light off is mandatory. During summertime one can place their hand outside and feel the cool inside air just funneling out the fireplace flue. The reverse is true in winter when the FP is turned off, warm conditioned air escapes out of the flue. A damper door would be nice but I've never seen them on gas direct vent FPs. |
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FBBP
Veteran Member
Posts:1215
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| 08 Apr 2013 11:08 AM |
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Lets take a look at OP's picture.
It has two pipes. The one in the middle (probably stainless) is the exhaust flue. The second pipe is wrapped around the first. Probably galvanized metal. Two pipes. no space between the exhaust and intake. That would take three pipes. I believe some direct vents might use a "B" vent for their outside pipe in which case it would be exhaust/intake/space. still no space between hot and cold.
Again looking at the picture, this appears to be a sealed combustion, "power vented" fire place. The power vent needs to prove air flow before the gas valve is allowed to open. I believe that today any fp that provides a reasonable amount of heat and is direct (horizontally) vent, needs to be power vented.
As a sealed unit, no critters will get into the house. |
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Lbear
Veteran Member
Posts:2740
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| 08 Apr 2013 07:20 PM |
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These photos will show that the flue is directly open to the outside as you can see daylight and it is a straight through design. If I removed the wire screen outside a rat could fit in flue and simply walk a few inches and fall into the fireplace. Once inside it can crawl through the bottom vented grate or where the top is vented and make its way into the home. The flue is simply sheet metal and as you can see they just tripped it out with metal snips. This FP is about 5 years old and the brand name is: "Majestic Direct Vent - MODEL DVBR46"    As you can clearly see, the pipe is straight through and the reason why you see that sheet metal at the end is the flue has that vertical sheet metal cover as seen in the previous post photo. |
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Dana1
Senior Member
Posts:6991
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| 09 Apr 2013 11:48 AM |
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Posted By Lbear on 04 Apr 2013 06:32 AM
Posted By nd96 on 04 Apr 2013 06:07 AM
I found details from the fireplace manufacturer. They recommend 1" around the pipe to any combustable materials. I think I might want a little more for EPS. I'd be a little concerned about the EPS starting to soften, then melt or drip onto the pipe (if it gets that hot). I'll check with my fireplace installer and ICF sub/rep to see what they say.
I would feel better with 2" and that is code in most counties. Check with your building department or they might make you redo it, which is not fun with concrete.
What you will want to do, even with a 2" gap between the flue and EPS, is to thermally protect the EPS from the 400F+ flue heat. Whether it's high temp fiberglass batts (not paper faced) or some other material, you have to keep the 400F+ temps from permeating to the foam.
Don't forget make up air with a tight ICF home. Even with natural gas fireplaces, they are still consuming interior oxygen and create a pressure effect. You don't want to create a negative pressure which can cause back drafts and carbon monoxide to channel back into the home.
IRC code specifies 2" clearance between flues & combustibles for masonry, 1" for double-wall (B-vent) but specifically dis- allows filling the gap with anything, except for non-combustible fire-blocking/air barriers (such as sheet metal) as necessary where it passes through walls. That said, it is a section of code that is violated all the time, but using only 1" of non-combustible insulation is probably a bit too skimpy, especially if fiberglass. Using 2"+ of rock wool batting is far preferable to high-temp fiberglass, since in a real fault condition fiberglass can melt, and fiberglass in thin layers will pass quite a bit of heat via radiation (it's translucent in the infra-red spectrum.) Rock wool is slag from steel-making with a much higher melting temp, and is opaque to IR. Cutting a ring out of the EPS concentric with the vent with 3-4" of clearance between EPS & vent, then filling it with rock wool batt scuplted & trimmed to fit snugly to both the vent & EPS cut-out would put R10+ between the vent and the EPS, yet preserve the net R-value of that small patch of wall. (Most rock wool batting runs ~R4.2/inch these days, about the same as Type-II EPS.) |
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theInvincible
New Member
Posts:74
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| 09 Apr 2013 05:54 PM |
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I did put Armour Plus 5/8 FireGuard between form and flue. I left more than 2". The flue is RSI 10. |
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FBBP
Veteran Member
Posts:1215
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| 09 Apr 2013 11:55 PM |
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Apples and oranges. OP posted a pic of a "reasonably" efficient glass fronted seal combustion chamber fireplace. You are showing an old below builders grade box for burning money. |
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nd96
Basic Member
Posts:111
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Lbear
Veteran Member
Posts:2740
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| 10 Apr 2013 05:01 AM |
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Awesome house and awesome ICF/concrete job! My wife (who is a schoolteacher) just read a book for her students, it was called " The Three Little Pigs:An Architectural Tale". In the end, it's the house of stone and concrete that remains standing. If the winds come howling, your house will endure. Enduring architecture, concrete structures that last hundreds of years. |
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nd96
Basic Member
Posts:111
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| 10 Apr 2013 05:23 AM |
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They say "A man's home is his castle". I admit, I may be taking that a little too literally. But I am having fun building my dream home and feel blessed to be able to do so.
It is something that will last the rest of my life, my children's lives, and probably quite a few years beyond that. Plus, the 8000sqft ICF with geothermal will be significantly more energy efficient and cost less to heat/cool than our current 2200 sqft conventional house. |
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dford
New Member
Posts:10
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| 10 Apr 2013 09:01 PM |
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nd96 are those current pics? I have been following your build...looks bad ass.....are you using a general? What's your completion ETA? I am going through Castle Rock in Phoenix. I too am building something I hope my kids will enjoy. More PICS! |
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nd96
Basic Member
Posts:111
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| 11 Apr 2013 06:46 AM |
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Posted By dford on 10 Apr 2013 09:01 PM
nd96 are those current pics? I have been following your build...looks bad ass.....are you using a general? What's your completion ETA? I am going through Castle Rock in Phoenix. I too am building something I hope my kids will enjoy. More PICS! I've been updating as we build, so they are the current pictures. I'll try to post more soon. I'm acting as my own general contractor and this is my first house. So far I have had good subs and things are going well. No regrets at this time. I took out a 12 month construction loan and started the house construction in January. I hope to have it dried in at 6 months (June-July) and finished out about the end of the year. I have a real job and family that keep me busy (we just had our 4th child 2 weeks ago), otherwise I might be able to finish earlier.   A couple more views from the outside.   A look at some of the bracing before the last pour. |
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nd96
Basic Member
Posts:111
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| 22 Apr 2013 11:28 PM |
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Time for an update. The attic floor pour is planned for Wednesday. After that, there is just the 3ft attic knee wall and tower left to do in ICF. There is a lot of steel (and concrete) going into this house.     The wagon wheel (circle) is where the 10 ft diameter skylight will go. The ICF tower walls will continue up another 16ft from there. |
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ICFHybrid
Veteran Member
Posts:3039
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| 23 Apr 2013 07:50 AM |
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How many workers is the ICF contractor running on a daily basis? |
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nd96
Basic Member
Posts:111
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| 24 Apr 2013 02:02 AM |
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Posted By ICFHybrid on 23 Apr 2013 07:50 AM
How many workers is the ICF contractor running on a daily basis? There is an ICF crew and a framing crew (2 different companies). Each crew has about 5 - 7 people. The framing crew changes up some week to week, but the ICF crew has been pretty consistent. They have both done a good job and I've been happy with their work so far. Things look good for the attic floor pour Wednesday AM. The ICF sub is estimating 120-130 yards. I'll post some updated pics later this week. |
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ICFHybrid
Veteran Member
Posts:3039
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| 24 Apr 2013 07:50 AM |
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The ICF tower walls will continue up another 16ft from there. So, how thick did the walls end up being at ground level beneath the tower? Are the upper portions of the tower walls 6" thick? |
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nd96
Basic Member
Posts:111
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| 25 Apr 2013 05:39 AM |
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Posted By ICFHybrid on 24 Apr 2013 07:50 AM
The ICF tower walls will continue up another 16ft from there. So, how thick did the walls end up being at ground level beneath the tower? Are the upper portions of the tower walls 6" thick? The walls and tower are all 6" concrete, except for the face of the garage. The columns between the garage doors are fairly narrow with a lot of wall above, so the engineer called for 12" forms there (just the 1st floor level). The attic floor pour went without any problems. It ended up right at 120 yards. The last 15 yards or so was actually for the cap on the 2nd floor balconies around the house. I had poured the balcony insuldeck joists separately from the cap in order to create a thermal break. I have over 100 linear feet (almost 1000sqft) of balcony on the 2nd floor, and I didn't want to spend the money for the Schöck Isokorb product discussed earlier this year, so I came up with my own design. We poured all the balcony joists (about 8" deep) with the 2nd floor pour, but left the balcony caps off. Then I came back and sprayed the tops of all the joists with a layer of closed cell spray foam. We poured the balcony caps with the standard rebar, plus we added fiber to the balcony concrete to give it a little more crack resistance. The process seems to have worked well and I think it will cut down on heat transfer by at least 75%.  (the exposed concrete joists before spray foam)  (balcony after spray foam and before the cap was poured) |
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nd96
Basic Member
Posts:111
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| 02 May 2013 02:39 AM |
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The final ICF pour is done! They did the full tower - 15' 9" (with a 6" observation deck/slab in the middle), and the attic knee wall on the same day.
Basically, they poured the bottom 1/2 of the tower, let it set a little while they did the 3' knee wall around the house, then came back and did the 2nd half of the tower.
I've got a really nice view from the top of the tower. Each of the octagon walls will get a functional double casement window, so I can open them up and make full use of the view.
I have absolutely no regrets about going with ICF or the sub I picked out. It was a very smooth process, especially considering this is my first time at building a house, and the complexity of the build. This is just my opinion, but I don't think you can over-estimate the importance of having a good, experienced, ICF sub - even with a basic design.
Tower from the outside, with the attic door access.
From the top looking down to the observation deck.
The whole thing looks a lot like a castle right now.
It's a long way down from the top.
That is the end of the ICF, but I've still got a long way to go before the house is done. I'll post an occasional update down the road, and maybe a video link if people are interested.
Thanks.
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ICFHybrid
Veteran Member
Posts:3039
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| 02 May 2013 07:56 AM |
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The final ICF pour is done! How many different days did the pump truck have to come out? I guess that is the same as asking how many lifts there were and did they use a pump truck for every one? |
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