# High Efficiency venting????? **URL:** \ **Category:** Inspecting HVAC Systems\ **Created:** [November 6, 2007, 1:30pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725 "2007-11-06T13:30:07Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Matt\_Lewis](https://avatars.discourse-cdn.com/v4/letter/m/e5b9ba/32.png) [@Matt\_Lewis](https://forum.nachi.org/u/Matt_Lewis)\ **Post date:** [November 6, 2007, 1:30pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/1 "2007-11-06T13:30:07Z")
Can anyone please site the exact venting requirements for High Efficiency Furnaces (and Tankless Water heaters if different). I have different contractors telling me that want to; vent directly underneath a raised deck or extend exposed pvc pipe 10’+ to get past the deck. Any help appreciated. ---
**Author:** ![cbottger](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/cbottger/32/206_2.png) [@cbottger](https://forum.nachi.org/u/cbottger)\ **Post date:** [November 8, 2007, 7:31pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/2 "2007-11-08T19:31:03Z")
> [@Matt Lewis](#): > > Can anyone please site the exact venting requirements for High Efficiency Furnaces (and Tankless Water heaters if different). > > I have different contractors telling me that want to; vent directly underneath a raised deck or extend exposed pvc pipe 10’+ to get past the deck. > > Any help appreciated. Sorry Matt no one was willing to jump on your post I have been waiting and must admit I had to go look at the code book. The only thing that I can come up with is that it states must be accessible for cleaning and maintenance and there is also a length requirement not to exceed I did not copy it down. ---
**Author:** ![jwilliams4](https://avatars.discourse-cdn.com/v4/letter/j/278dde/32.png) [@jwilliams4](https://forum.nachi.org/u/jwilliams4)\ **Post date:** [November 8, 2007, 7:43pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/3 "2007-11-08T19:43:28Z")
Contact the local AHJ…it may vary from town to town. It seems to here, anyway. ---
**Author:** ![mlarson](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mlarson/32/89225_2.png) [@mlarson](https://forum.nachi.org/u/mlarson)\ **Post date:** [November 8, 2007, 7:48pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/4 "2007-11-08T19:48:23Z")
It’s usually best to consult the manufacture’s installation instructions as they are the one’s that had it tested to accepted standards. ---
**Author:** ![jwilliams4](https://avatars.discourse-cdn.com/v4/letter/j/278dde/32.png) [@jwilliams4](https://forum.nachi.org/u/jwilliams4)\ **Post date:** [November 8, 2007, 7:49pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/5 "2007-11-08T19:49:43Z")
> [@mlarson](#): > > It’s usually best to consult the manufacture’s installation instructions as they are the one’s that had it tested to accepted standards. Oh, yeah. That, too… ---
**Author:** ![mlarson](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mlarson/32/89225_2.png) [@mlarson](https://forum.nachi.org/u/mlarson)\ **Post date:** [November 8, 2007, 7:50pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/6 "2007-11-08T19:50:23Z")
> [@jwilliams4](#): > > Oh, yeah. That, too… I knew you knew that Jae:D ---
**Author:** ![phinsperger](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/phinsperger/32/553_2.png) [@phinsperger](https://forum.nachi.org/u/phinsperger)\ **Post date:** [November 9, 2007, 12:45am UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/7 "2007-11-09T00:45:14Z")
If your in a climate zone that experiences freezing temperatures I wouldn’t be extending it 10’ under the deck ---
**Author:** ![Brian\_A.MacNeish](https://avatars.discourse-cdn.com/v4/letter/b/90db22/32.png) [@Brian\_A.MacNeish](https://forum.nachi.org/u/Brian_A.MacNeish)\ **Post date:** [November 9, 2007, 5:22pm UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/8 "2007-11-09T17:22:45Z")
> [@phinsperger](#): > > If your in a climate zone that experiences freezing temperatures I wouldn’t be extending it 10’ under the deck Or insulate it and slope it to drain condensation. ---
**Author:** ![wdecker](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/wdecker/32/174659_2.png) [@wdecker](https://forum.nachi.org/u/wdecker)\ **Post date:** [November 10, 2007, 4:31am UTC](https://forum.nachi.org/t/high-efficiency-venting/21725/9 "2007-11-10T04:31:51Z")
> [@mlarson](#): > > It’s usually best to consult the manufacture’s installation instructions as they are the one’s that had it tested to accepted standards. Local codes usually mean nothing with cat 4, high efficency furnaces. the manufacturer’s installation instructions rule (except where the local codes are stricter, which never happens). i have gone up against Chicago building code inspectors, many times, and they are not aware of the new 90+ requirements (Gee, think CE should be required for local building code inspectors? 😉 ). Remember, a 90+ furnace with no combustion air intake is only 80+. Allowed, but not now it was designed. Make sure that the PVC vent pipes have screens. Many past clients are complaining about roasted birds, now that they are running the furnaces. :shock: Call me (see below) if you need to. Hope this helps;