Condo Conditioned Crawlspaces – Ventilation?
whatever419
| Posted in Energy, Heating & Insulation on
Our condo HOA has hired a contractor to condition the crawlspaces in our attached 2 story 20 year old buildings located in south central Indiana (Bloomington). We have four connected first floor units that will be most impacted by the upgrade. The crawlspace below each unit measures approx. 1000 sq ft., but I believe all are connected via (just guessing) approx. 10′ opening in support walls between units. The space below my unit is very shallow, approx. 16-24″ high. So, rounding things off- 2000 cu ft under each unit x 4 units = 8000 cu ft total crawlspace.
A new vapor barrier is being installed over the old and blueboard insulation placed on the cinder block walls. Some sort of sealing is being done to the floor joists and exterior vent blocked off with blueboard.
In the middle of each first-floor unit, a gas furnace is in a utility closet which opens into the great room. It has a 6×12″ floor vent into the crawl space to draw combustion air for the furnace. I was told by a worker, if they don’t have this vent, one will be installed so that “air will circulate to the crawlspace.” I don’t understand this.
If our living space is always warmer than the crawlspace, how will air move down?
And if it did move down, would this small passive opening, be enough to take care of possible humidity/mold issues?
Finally, with the crawlspace being sealed from the outside, will there be sufficient air for the furnaces?
Replies
You have a valid question about "make up air" for the furnaces, vent fans, et al. There generally should be a vent to bring outside air into the space near the furnace -- whether the crawl qualifies as "outside" once sealed is questionable. At the very least, there should be an outside air vent into the crawl, and ideally the vent duct from outside should be brought into the furnace closet.
Several Problems
There are several problems with the condo association's plans.
First, for a crawlspace to be installed as 'unvented', it must have a vapor sealed floor, be insulated on the exterior walls, have no openings to the exterior, and be supplied with mechanically 'conditioned' (IE heated/cooled/dehumdified) air or have a vent that allows the crawlspace to naturally communicate with conditioned space above.
Second, you will no longer be able to use this space to supply combustion air for the furnaces because A) there will no longer be fresh air to supply the combustion air and B) you cannot take combustion air from or use a crawlspace as a plenum when it contains exposed plastic insulation. New combustion air supply ducts will need to be installed directly to the exterior of the building. These ducts can go through the crawlspace but cannot take any combustion air from the crawslapce.
Thirdly, there may be fire separation issues between units unless each unit's crawlspace is not also sealed from the other crawlspaces.
In most instances, an architect or engineer would be required to design the alterations for a commercial project of this type and these plans would be required to be submitted to your building department for Code compliance plan review before a permit could be issued.
The items listed above could pose life safety code violations and need to be answered and addressed by your HOA before this project is given a green light.
The interconnected crawl spaces and exposed blueboard are your serious issues as noted. Imagine the conditions with a fire in the crawl space (toxic gas) and an HVAC unit fan pulling into living space.
Crawl to be heated! But where the air?
Clarifications & News:
* Turns out our crawlspaces are connected in pairs (not all 4 together).
* Vents will not be cut in floor, but don't know if they intend to cover existing ones (when we got a new furnace & our vent was sealed and a pipe installed directly from combustion chamber to crawlspace).
* A duct will be installed on the plenum of each furnace to direct heated/cooled air into crawlspace. I don't know of any plan to replenish extra air required for this.
* OwensCorning FOAMULAR 150 2" rigid extruded polystyrene insulation is being installed.
* The ducts in the crawl are flex type (don't know about insulation).
* I am awaiting info on local regs re connected crawlspaces...
Needless to say, I have more questions about heating the crawlspace - especially since it connects to my neighbor. The mgmnt company rep sent me "conditioned crawlspace" info that extolls the advantages of (essentially) heating our floor. But since our floors are probably osb or plywood and covered with carpet, how much good is it going to do for the living space?
My wife spoke this morning on the phone to our HVAC guy (before we knew the stuff above) and he seemed to think they will not get the crawl tight enough to cut combustion air. I dunno...
Thanks for all the input - a great help.
Architect or Engineer Required
An architect or engineer is normally required to design the changes for a job of this type on a commercail building and stamped plans required to get the needed building permits.
Unfortunatley, it sounds like there is no professional designer and those involved are flying by the seat of their pants and quite blindly.
1. The crawslpace must be made tight and sealed against all outside air for it to be an unvented crawlspace by Code.
2. If the furnaces were drawing combustion air from the exterior through the crawlspace via open vents to outside air, there certainly will not be enough combustion air available from the sealed crawlspace for the HVAC system to work properly. Especially since the 2 crawlspaces will also need to be separated from one another. New direct combustion air vents must be installed to the exterior to each HVAC unit. Combustion air cannot come from the crawlspace..
3. Foamular 150 is FLAMMABLE. There can be no open vents from the living space to a crawslpace or attic in which Foamular insulation is installed. The HVAC system cannot draw combustion air from a crawlspace in which such rigid foam insulation is used, nor can return air come from this space where rigid foam insulation is installed. The exception is if an ignition barrier like drywall, plywood, metal or similar material covers the Foamular insulation.
Start talking to professional designers and your local building code plan reviewers before you talk further to any contractors.
He IS talking to a professional designer ... ;o) and, you're right.
professional designer?
OK, I guess the "professional designer" was tongue-in-cheek. Right?
Ummm
I meant ME.
1, 2 & 3 questions
1. I do not know what the code is here re unvented crawlspace or what the final plan for the space is. Hope to find out today.
2. It is highly unlikely they will separate the crawlspaces - unless forced by law.
3. Why do you say "The HVAC system cannot draw combustion air from a crawlspace in which such rigid foam insulation is used"?
3. Why do you say "The HVAC
3. Why do you say "The HVAC system cannot draw combustion air from a crawlspace in which such rigid foam insulation is used"?
Exposed foam = fire risk with toxic fumes
Used for makeup air = potential to bring toxic fumes into living space
"Used for makeup air = potential to bring toxic fumes into living space"
Under day to day normal conditions? Or do you men if/when it burns?
I am still trying to get info re local regs and HOA's plans.
Re the connected crawls, from a practical standpoint they do not pose (much of) a fire spread hazard, since heat rises and, in the most likely scenarios, a fire would draw air into the crawl rather than push flames out. This is much different from connected attics, where there is a serious chance of fire spread.
Code may or may not take this into account. Certainly connected basements are common in lots of older multi-unit buildings.
You are right to be at least concerned. The other posters have definately provided food for thought. We could probably discuss the benefits of a sealed and/or conditioned crawlspace at great length. A sealed crawl should be a good thing. Greatly reduces heat loss through the floor ... possible summer benefits, too. The concept is reasonable. However a sealed crawl isn't the same as a conditioned crawl ... two very different animals.
A little confusing about the vents to the crawl - combustion or conditioned ... or both?? I understand you to say that the intent is to put e.g. a single vent in the floor to provide the combustion make-up air for the furnace.
As others pointed out ... exposed polystyrene insulation would not be allowed w/ any vent in the floor. Code requires it be covered with a fire material in 'substantial contact with the insulation' (such as drywall).
If the intent is to provide combustion air, that will likely help keep humidity levels to a minimum in the crawl. Any air exchange will tend to lower the humidity levels. Practically, drawing combustion air from the space might be a reasonable thing to do. You can't/shouldn't expect to draw it ONLY from a sealed crawl. Another option is to duct the combustion air to the outside w/ a motorized damper interlocked w/ the furnace. It would have to dump into e.g. a combustion air plenum to the furnace.
Your house supply and return is ducted under the floor? or ducted supply and return directly to the furnace??
I'm surprised that the crawls of the two units are connected. Seems like a major fire code issue (although I'm not an expert). If I recall, all units of multifamily residential must be separated by e.g. a 1 or 2 hour fire separation wall. Maybe this was OK before, but opening the crawl to the house may cause an issue.
You/the HOA should be talking to a license professional - architect. Respectfully, your contractor guy may have some reasonable ideas, but the execution has to be done right. I detect some potentially serious fire code issues with some of the stuff you said and it at least warrants a reality check by someone who knows. I assume he's going to permit this. A BO should spot any glaring issues ... and may require an architects stamp anyway. Sealing a crawl in itself can be a code issue if not handled properly.
Keep us posted.
slow going & extruded polystyrene insulation
I will definitely post the progress and outcome of this project. Since it has been very slow going getting a comprehensive view of what is actually proposed, at this point I am reluctant to answer any more questions here. I hope to have a better picture by tomorrow (fingers tightly crossed).
That being said, I'd like to ask a question: If OwensCorning FOAMULAR 150 2" rigid extruded polystyrene insulation was not the best choice for this job, what would have been better?
Thanks to all.
Not sure what you are asking. Didn't think that anyone had a negative comment on insulation choice ... just that given the situation, there may be other issues associated with the material chosen. ANY polystyrene, if there are issues, will be in the same boat ... Whether extruded or expanded polystyrene or whether polyiso or a urethane ... they all need protection, although a foil faced polyiso MAY have a rating that is acceptable ... depending on how it is applied/used.
OwensCorning Foamular vs ?
As others have mentioned, rigid foam insulations, including Foamular, are flammable and are required in most cases (generally speaking) to be covered with a thermal barrier to prevent igintion in a fire.
Such barriers include drywall, structural sheathing, sheet steel, and fire retardant coatings....all of which are expensive.
There is only 1 rigid foam insulation on the market today that is tested and listed to be installed without an ignition barrier:
Dow TherMax. See the International Code Council evaluation report below which states:
"A thermal barrier is not required to separate TheMax boards from the interior of the building or structure."
http://www.icc-es.org/reports/pdf_files/NES/NER681.pdf
You are right to be at least concerned. The other posters have definately provided food for thought. We could probably discuss the benefits of a sealed and/or conditioned crawlspace at great length. A sealed crawl should be a good thing. Greatly reduces heat loss through the floor ... possible summer benefits, too. The concept is reasonable. However a sealed crawl isn't the same as a conditioned crawl ... two very different animals.
A little confusing about the vents to the crawl - combustion or conditioned ... or both?? I understand you to say that the intent is to put e.g. a single vent in the floor to provide the combustion make-up air for the furnace.
As others pointed out ... exposed polystyrene insulation would not be allowed w/ any vent in the floor. Code requires it be covered with a fire material in 'substantial contact with the insulation' (such as drywall).
If the intent is to provide combustion air, that will likely help keep humidity levels to a minimum in the crawl. Any air exchange will tend to lower the humidity levels. Practically, drawing combustion air from the space might be a reasonable thing to do. You can't/shouldn't expect to draw it ONLY from a sealed crawl. Another option is to duct the combustion air to the outside w/ a motorized damper interlocked w/ the furnace. It would have to dump into e.g. a combustion air plenum to the furnace.
Your house supply and return is ducted under the floor? or ducted supply and return directly to the furnace??
I'm surprised that the crawls of the two units are connected. Seems like a major fire code issue (although I'm not an expert). If I recall, all units of multifamily residential must be separated by e.g. a 1 or 2 hour fire separation wall. Maybe this was OK before, but opening the crawl to the house may cause an issue.
You/the HOA should be talking to a license professional - architect. Respectfully, your contractor guy may have some reasonable ideas, but the execution has to be done right. I detect some potentially serious fire code issues with some of the stuff you said and it at least warrants a reality check by someone who knows. I assume he's going to permit this. A BO should spot any glaring issues ... and may require an architects stamp anyway. Sealing a crawl in itself can be a code issue if not handled properly.
Keep us posted.
Another thought ... the contractor should get a permit and the BO may/should require a architects stamp when making changes that might affect the fire/health safety of the condo. Again, if the floors are part of the fire rated enclosure and now they are punching holes, and the two units crawls are connected, this could be a major issue. Worth a double check and second opinion, for sure.
Pre-Thanksgiving UPDATE:
We learned for the first time from a worker that a duct would be installed to the plenum on the bottom of our furnace to supply conditioned air to the crawl.
Email reply from county buildings department:
* "Apartment construction allowed crawlspaces to be connected assuming that the floors over the crawlspace had a one hour floor/ceiling assembly..."
* "combustion air grills should be fitted with a fire damper"
* "foam plastic insulation shall be protected against ignition..." (I have heard fire-retardant paint will be acceptable)
* crawl "shall be continuously supplied with a minimum of 1.0 Cubic Foot per Minute of conditioned air per 50 Square Feet of under floor space"
* "No permit is required."
Question to forum:
Apprx 1000 sq ft crawlspace- so, 1 CuFt x 20 = 20 cu ft/min? How do I find out if our furnace/AC is delivering this?
We have a newly installed Bryant Evolution System Plus 95s Gas Furnace. Some (most?) of our neighbors will have 19 year old, less efficient furnaces.
We met with 3 members of our HOA board re the crawlspace remediation -
Q: Who is the designer/expert of the crawlspace modifications?
A: A professional crawlspace remediation company submitted a line item bid. It was very high. They copied the line item list and submitted it to (2?) other companies.
Specific questions about the design (how return air would get back from the crawlspace to the furnaces, etc.) were met with the same answer: The work is being done properly and "according to code."
Q: Are you going to ask the other owners for permission to alter their plenum/heating system?
A: No response. Their basic reply to these type questions was that the crawlspace upgrade was approved at the July membership meeting. That no minutes have been distributed and that numerous members missed the meeting did not appear to concern them.
This job apparently does not require inspection by building department, but (we think) the HOA agreed to ask if the department would be willing to do it if asked.
We said our concern was about whether our furnace would still work efficiently and also concerned about the quality of the air we will be breathing.
Sorry if I haven't addressed all questions posted here (figgered this post was overly long already).
"According to code"
... Is not an answer. "Specific questions about the design (how return air would get back from the crawlspace to the furnaces, etc.) were met with the same answer: The work is being done properly and "according to code.""
Your question was how would it be done, not whether it would meet code.
Never heard of fire retardant paint that could be used on polystyrenes to provide the required flame spread and smoke development ratings stated in codes.
Undistributed minutes to missing members could be a key item for problems later when some of the other members don't like the half baked approach the contractor may be using.
I'm surprised a permit isn't required to punch a hole in a fire rated assembly and alter the characteristics of the heating system like this.
Still think the services of an architect might be worth the expense to ensure someone is taking the liability for this modification. The contractor ... a crawlspace remediation contractor ... whatever that is ... may know little about the air flow issue. Also how does he plan to protect the polystyrene?
punch a hole in a fire rated assembly?
"I'm surprised a permit isn't required to punch a hole in a fire rated assembly and alter the characteristics of the heating system like this."
By "fire rated assembly" do you mean the furnace?
The local Planning Dept. has been answering some questions and suggesting options. He told us that if they change from a vented space to a conditioned space, a permit and inspection would be required. Is it your opinion that the Planning Department inspectors would inspect the duct and fittings installed to direct conditioned air to the crawl?
There are so many new wrinkles in this drama, I have started a new thread at -
http://forums.finehomebuilding.com/breaktime/energy-heating-insulation/condo-crawl-space-dilemma-continues
Thanks.
by 'fire rated assembly', I mean e.g. a wall, floor, etc. designed to provide separation between e.g. units in the condo. It's code speak for separation between different areas of the building to control the spread of a fire.
Not really a 'planning' issue IMO. It would be the building department and yes, the building inspector would inspect any aspect of the proposed changes that are controlled by building life safety codes whether it be ducts or materials of a fire rated assembly (or the method chosen to penetrate/alter that assembly).