Unheated Vented Crawl Space Insulation - Insulation - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Insulation

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Like Tree2Likes
  • 1 Post By Bud9051
  • 1 Post By Cooner
Reply
 
Thread Tools Search this Thread
Display Modes
Old 10-02-2018, 03:51 PM   #1
Newbie
 
Join Date: Oct 2018
Posts: 3
Rewards Points: 6
Default

Unheated Vented Crawl Space Insulation


Hi All,

Thanks for taking the time to read my thread. My wife and I bought a cabin in the foothills above Seattle, Sultan to be exact - marine climate zone 4. The cabin was built in the 70's. It does not have any HVAC but is heated by wall heaters and a wood burning stove. The crawl space is vented and with no HVAC, not heated. It has some significant rot in the floor joists and floor due to moisture. We ripped it down to joists to see how bad and it is bad, but fixable. It doesn't, but will have a vapor barrier on the dirt floor of the crawl space.

So, my question. I see everywhere that the best thought now is to encapsulate the crawl space, vapor barrier on bottom, rigid foam insulation for the concrete foundation walls, seal the vents and then heat it. I don't know how to heat it it we don't and won't be putting in a HVAC system. With that thought, I thought it would be best to leave it unheated, vented, put a dehumidifier down there and then insulate under the floor between the joists. We planned on using Rockwool with mesh retainer at the bottom of the joists. I thought to avoid air and moisture transfer into the house I thought about putting a vapor barrier on top of the joists before laying the subfloor.

Can anyone please advise me as I really don't know the best path and need to prevent continued damage?

Thanks,

Cooner
Cooner is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 10-02-2018, 04:05 PM   #2
retired framer
 
Join Date: Jun 2017
Location: Fraser Valley BC Canada
Posts: 38,070
Rewards Points: 750
Default

Re: Unheated Vented Crawl Space Insulation


Quote:
Originally Posted by Cooner View Post
Hi All,

Thanks for taking the time to read my thread. My wife and I bought a cabin in the foothills above Seattle, Sultan to be exact - marine climate zone 4. The cabin was built in the 70's. It does not have any HVAC but is heated by wall heaters and a wood burning stove. The crawl space is vented and with no HVAC, not heated. It has some significant rot in the floor joists and floor due to moisture. We ripped it down to joists to see how bad and it is bad, but fixable. It doesn't, but will have a vapor barrier on the dirt floor of the crawl space.

So, my question. I see everywhere that the best thought now is to encapsulate the crawl space, vapor barrier on bottom, rigid foam insulation for the concrete foundation walls, seal the vents and then heat it. I don't know how to heat it it we don't and won't be putting in a HVAC system. With that thought, I thought it would be best to leave it unheated, vented, put a dehumidifier down there and then insulate under the floor between the joists. We planned on using Rockwool with mesh retainer at the bottom of the joists. I thought to avoid air and moisture transfer into the house I thought about putting a vapor barrier on top of the joists before laying the subfloor.

Can anyone please advise me as I really don't know the best path and need to prevent continued damage?

Thanks,

Cooner
The dirt floor is your biggest problem so sealing the ground only works if there is no water leaking in anywhere. Conditioning the space is a little had with out a forced air system.
There are charts for the amount of venting and placement of the vents, you may want to find. I am not a believer but others will be along to tell you how wonderful encapsulation is.
The floor is considered the vapour barrier and all holes and leaks between the space and the house should be sealed. I would insulate it as you described. The poly on the dirt wants to be sealed to the foundation so no moisture can come up.
Nealtw is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 10-02-2018, 05:28 PM   #3
Member
 
Join Date: Nov 2015
Location: Maine
Posts: 10,706
Rewards Points: 214
Default

Re: Unheated Vented Crawl Space Insulation


A dehumidifier in a vented crawlspace wouldn't work very well.

Neal and I dance around with this topic as I like an encapsulated space, HOWEVER, as you stated providing heat down there would be a must and during the warmer months an encapsulated space would also share the ac, ac is a dehumidifier.

Do you live in this cabin year round or is it seasonal?

When I want cold climate guidance I often find it good to look farther north, Alaska. They have for many years been aggressive in their approach to energy efficiency Here is an article I have only skimmed a few years ago and no time to go through it now, but it has a good title "Crawlspace Ventilation from the cold climate housing research center". http://www.cchrc.org/sites/default/f...ntSnapshot.pdf

Take a look and I'll check back, probably tomorrow.

Bud
Nealtw likes this.
__________________
I volunteer my help and opinions, but you are responsible for what YOU choose to do with that information.
Bud9051 is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old 10-02-2018, 05:38 PM   #4
Newbie
 
Join Date: Oct 2018
Posts: 3
Rewards Points: 6
Default

Re: Unheated Vented Crawl Space Insulation


We aren't there year around yet, but plan to be.

Fortunately, there really are no leaks. The dirt in the crawl space is dry as are the walls, it seems like it's purely ambient moisture.
Cooner is offline   Reply With Quote
Old 10-02-2018, 05:51 PM   #5
retired framer
 
Join Date: Jun 2017
Location: Fraser Valley BC Canada
Posts: 38,070
Rewards Points: 750
Default

Re: Unheated Vented Crawl Space Insulation


Section R408.1, Ventilation The first paragraph of IRC section 408 provides the standard requirement for ventilating crawlspaces:






The under-floor space between the bottom of the floor joists and the earth under any building (except space occupied by a basement) shall have ventilation openings through foundation walls or exterior walls. The minimum net area of ventilation openings shall be not less than 1 square foot for each 150 square feet of under-floor space area, unless the ground surface is covered by Class 1 vapor retarder material. Where a Class 1 vapor retarder material is used, the minimum net area of ventilation openings shall be not less than 1 square foot for each 1,500 square feet of under-floor space area. One such ventilating opening shall be within 3 feet of each corner of the building


Section 308.3, Unventilated Crawlspaces
This paragraph makes provisions for situations in which builders and homeowner prefer to omit vents in crawlspaces, usually because they wish to prevent thermal heat loss or to prevent insects and other vermin from gaining access to the space.






In the most recent edition of the IRC, builders are now allowed the option of creating non-vented crawlspaces, provided they follow the following procedures:





  • Mechanically circulating air is established between the upper conditioned area of the home and crawlspace. The air-circulating device must move at least 1 cubic foot of air per 50 square feet of crawlspace area.
  • The crawlspace floor area must be completely sealed with a vapor-retarding material. This means lapping the edges of the vapor retarder up against the inner foundation walls, overlapping separate sheets by at least six inches, and sealing up those seams.
  • All crawlspace walls must be insulated to appropriate R-values for the regional climate.

https://www.thespruce.com/crawlspace...ements-1821946
Nealtw is online now   Reply With Quote
Old 10-02-2018, 06:16 PM   #6
Newbie
 
Join Date: Oct 2018
Posts: 3
Rewards Points: 6
Default

Re: Unheated Vented Crawl Space Insulation


Thanks All. So, the previous owner had sealed two vents on one side of the cabin with insulation and left the two vents on the opposite side open. They are large enough and close enough to the corners based on my observation.

So, I think I need this list - vapor barrier on the dirt floor and sealed on the concrete foundation walls, open all of the vents, dehumidifier may not help much, but couldn't hurt, insulate without any vapor barrier between the joists, then maybe vent fan(s)?

I know it is stating everywhere encapsulate the crawl space, but given I won't have any forced air, I'm trying to do all I can while leaving the vents open.
Nealtw likes this.
Cooner is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply

Tags
crawl space insulation , no hvac , unheated , vented


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Crawl Space Insulation Crosby.Photo Insulation 2 04-05-2017 01:47 PM
Crawl Space Insulation Advise Needed BayouRunner General DIY Discussions 5 09-11-2016 04:25 PM
Bad smell in crawl space. John_W General DIY Discussions 34 06-03-2014 12:57 PM
Vented crawl space insulation gregsenne Insulation 9 10-10-2012 02:56 PM
Unvented crawl space insulation ehardman Building & Construction 3 01-13-2009 12:44 PM




Top of Page | View New Posts