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Karli Pritchett Posted: May 16, 2010 10:16 PM	High humidity level in spray foam house I just had a house built with spray foam and have been living in it for less than one year. Throughout the winter I have had excessive condensation on my windows to the point of ice inside the house on the windows. I have mold growing in almost every window in my house. I found my humidity level was almost 70%! I've had one "expert" tell me I need vinal windows instead of aluminum, and another tell me I need an energy recovery ventilator, and a central dehumidifier. The builder has made no effort to help me figure out how to solve this problem. I have done a lot of research on the internet and can't find anyone who agrees, or knows for sure how to fix my problem. I need to know what will fix my house? Please help!
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: May 17, 2010 07:25 AM	It sounds like the foam did a great job at sealing up the house - as it was supposed to! So, the question is where is the moisture coming from???? Is the basement floor water proofed? Are the basement walls water prrofed? Tehse are the tow most common areas of mositure migration!!
mason Posted: May 17, 2010 09:47 AM	You have to find the source of the moisture and then reduce the amount of moisture coming into the house and increase the amount of moisture leaving the house. 70% humidity level is very high even for a well sealed home. Some things to look for. Mechanical vents in kitchen, bathrooms and laundry rooms should in good working order and vented to the outside. Sometimes contractors take the vent ducts to the attic instead of to the outside. (Remember you have to turn them on in order for them to be effective) People, pets and plants (aquariums too) provide a lot of moisture in a building. The more you have the more moisture is created. As Jim suggests, check the basement and foundation walls. At first glance it would appear a ERV would be in order if the moisture build up is due to the house being extremely tightly sealed. Get an building science expert to check out the house and make recommendations. Get a professional in to
Karli Pritchett Posted: May 17, 2010 09:51 AM	I live in east Texas, and we have no basement. We have central heat and air. Yes, the spray foam has sealed the house tight, but the builder is not educated in how to properly ventilate the house. I have also been told that a fresh air vent would solve this problem. The humidity level right now is at 49%. But, it is summer in Tx and the a/c is running. I am positive this high humidity level will return in the winter. I was cooking a pot of beans yesterday, and so they were constantly boiling, letting off humidity, and even though I had the vent a hood on the whole time, my humidity level got up to 58%! Once the beans were turned off, the humidity came down. I've done research on how much humidity we should have, and take all the right steps. Our house is 1957 sq.ft and only 2 adults and a baby live here, we aren't letting off more humidity than the house should control, and my husband checked, we have no water leaks! The only problem I can figure is the house is sealed so tight, only so much humidity can be sucked out, no fresh air is coming in to make up for what's going out. The builder's answer is that it is normal and will go away after a year. WRONG! Please help!!
mason Posted: May 17, 2010 10:20 AM	Get a HVAC contractor that knows sprayfoam applications to take a look at the house and the current ventilation situation. From what you describe, additional ventilation is required to reduce your humidity. They should be able to calculate the size and type of ERV to help out your situation. The units typically can be installed into your current duct system. Costs vary but I would estimate around $1500.
Karli Pritchett Posted: May 17, 2010 10:43 AM	I have had 3 HVAC experts! The first one said to change the windows from alluminum to vinal and that would fix the problem, I did research, and I disagree, until the humidity problem is solved any window will sweat! The second did a blower door test that was acceptable, and said I needed an ERV, and a central dehumidifier, total estimate, $9,250!! I did some more research and am thinking an ERV defeats the purpose of a spray foam house. The one they would install was going to exchange the air in my house 8 times a day! How is that efficient? Also, I read HVAC guys love to rake you over the coals w/these ERV's even if they're not really neccesary. Finally the third says a fresh air vent, like they install in houses with fireplaces, which I do not have, would fix the problem. I'm now thinking that is the smartest solution, new, fresh air would only be sucked in only when needed to let air out, like fom my exhaust fans! By the way, my fans are all vented to the outside, and I always use them! I'm thinking though, that I also need a central dehumidifier to contol any extra the house can't get rid of! That's the biggest part of my problem, I just wanted to build a great, energy efficient home that I would live in for the rest of my life. Not even a year and I have a MOLD problem, and from what I read even the excessive humidity levels aren't good for me or my house, and I have a baby!! I believe I'm looking in the right direction, only problem is EVERY EXPERT has a DIFFERENT opinion! Since the buider really isn't that educated in this area, I am having to educate myself. Every where I look, different answers! I just want the best way to permenately fix my house!!
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: May 17, 2010 11:17 AM	So, it sounds like it's a slab on grade type of construction??? What do you have for a floor finish material? Carpet? How much carpet? An ERV or some other mechanical device only tries to eliminate the symptoms,not really addressing the root cause. The Root Cause is that you have too much moisture coming in the hoem from somewhere. I would suspect it's coming in through the slab whcih is why your builder said it will go away in about a year or so!!! There is another product out there which can be used for slab on grade type of applications that it will work as a carpet pad and a moisture barrier all in one! We've used it many time as carpet padding or under the concrete as a vapor barrier and have not had a problem. If you want to email, me I can give you the name and can hook you up with a distributor of the product.(jim"at"coler.com) I agree with your mindset that you're addressing the symptom and not the root cause! Your moisture level should be about 30-50% year round with a family of 3 in a 2000+/- house! JIm Coler
Karli Pritchett Posted: May 17, 2010 11:33 AM	We do have a slab on grade constuction. We have 1392 sq. ft. of carpet and carpet cushion and 523.20 sq. ft. of sheet vinyl(linoleum). The builder is saying it goes away in a year because he built his daughter a foam house a couple of years ago, and said hers sweat the first year then it went away. Only, she never had excessive moisture that caused mold! So every house isn't the same. There is a house about 2 miles from mine that he built and she is having the exact problem. Her house was built in the winter and her mold problem is even worse than mine! I believe he is saying it will go away after a year because that is when my warranty gets limited! I have also researched that amount of moisture a new construction house has is a little more than normal due to the wood, carpet, etc. letting out the moisture that may have been soaked in during the building process, however I just don't see the slab causing THAT much moisture, wouldn't my floors be at the least moist? From what I have learned, there is absolutely NO excuse for my humidity level to have ever been that high! The high humidity didn't go down until the ac was turned on for a while, I believe that when winter rolls around and the heater is back on we will have the exact same problem. More suggestions please!
Karli Pritchett Posted: May 17, 2010 02:23 PM	It seems like 50% of the people you talk to are for and 50% are against spray foam houses. Most that are against it are people with problems like mine. I think it's still fairly new to most and there are no set rules on ventilation, at least none that I can find. I wish someone knew or could figure out the right specs for builders to have to know and follow when using spray foam. Spray foam was highly recommended to us and we were excited, but it seems lack of education and regulations on spray foam houses has ended up hurting us. It has been highly recommended to us by many sources that we take our builder to court, but thats not what I want. I just want to figure out from someone with credentials and authority to give me a solution that I could take to the builder and say this is the answer GUARANTEED!! Then give the builder the option to comply with something I actually had definate proof would work!! Anyone have any answers?
mason Posted: May 17, 2010 02:49 PM	I teach courses on the application of SPF for the building envelope. There are 2 chapters on building science principles and design. We recommend that the sprayfoam contractor partner with a HVAC contractor to make sure the home is sealed and ventilated correctly. One problem is that most homes are so leaky (even new construction) that HVAC contractors assume that the house will have a greater amount of air exchanges per hour than it actually has. The furnaces, vents, intake air and air conditioners must be sized correctly to account for the air tightness of the home. So that is why it is important for the sprayfoam contractor and the HVAC contractor to discuss the relative air tightness of the house based on the type of construction, type of windows, and where the foam is installed. As a rule of thumb the HVAC contractor should assume the SPF insulated house (walls and ceiling) should have around 30% to 50% greater air tightness than a house without the foam. For example if the HVAC contractor assumes a .55 air exchanges per hour, the SPF would most likely tighten it to .20 air exchanges per hour (on a new home) On existing homes where the SPF would be installed in the attic and basement only, the relative air tightness would be less and most likely would not require additional intake air. But in new homes, you would most always require additional air. Still, the home builder should be responsible for this snafu. If they knew the SPF was being installed they should know that additional air would be required.
Karli Pritchett Posted: May 17, 2010 03:29 PM	In my opinion, that is why I hired the builder. He suggested spray foam to me and all the benifits, no negatives. I figured he as the builder would know how to build my house properly, I knew nothing about building a house or spray foam. I figure I paid him to know these things for me, guess I was wrong. The blower door test showed the amount of leaks were acceptable for a house of my size. We have a tree ton ac and all three expert who have done a manual j on my house have told me that is ok. The one thing they all agree on! I have learned all of this stuff over the last few months, normally I would have no idea what a manual j is! One of the things that is so frustrating to me is that the builder doesn't seem concerned with what a problem this is coming for me and about 7 other homes that I know of that he has built. I trusted he knew what he was doing with spray foam seeing as how he put it in his daughters house. Come to find out, we are only the 2nd or 3rd house he's ever done this for. Mason, please tell me what your suggestion for my house is. Are you saying you think the fresh air vent would work? Do you think we also need the central dehumidifier, and is an ERV really neccesary in my case?
John Shockney Posted: May 17, 2010 05:07 PM	The first thing I see from your info is that this is a slab on grade construction probably with a moisture barrier underneath, when concrete dries the water has to go somewhere and it can’t go down so it comes up into the house, as a rule it takes 6-12 months for concrete to fully dry depending on weather and still could have a large water content after that in fact concrete cures getting harder over many years. You could verify that the moisture is coming from the slab with a moisture meter. The floor may not seem wet but still have water evaperating from it. If this is the case the only way to solve the root problem will be time. As an HVAC contractor I would probably recommend a Heat Recovery Ventilation system connected to the bath vents and controlled by a humidistat this would provide the make up air that you may be lacking when running the exhaust fans. This would relive the moisture problem in the winter without loosing energy savings. 2nd I would recommend a thermidistat (thermostat/humidistat combination) and connecting a dehumidify cycle to your AC, all this does is slow down the blower speed lowering the coil temp and removing more moisture from the air, this only runs in the summer when an HRV may bring in more moisture than it takes out depending on weather conditions. This is an inexpensive fix that most new HVAC equipment has built into it. And yes you could bring a fresh air vent into the house but remember to have a P or S-trap installed (like in plumbing) to keep excessive cold air out. Also make sure that you HVAC system isn’t oversized and short cycling this can effect the humidity. I started writing this before your last post and would say if manual J called for 3tons I would have put in a 2.5 ton AC or a 2 speed 3 ton heat pump with electric or gas furnace backup (the most economical system). In short your AC if properly sized should run 75-80% of the time during the hottest days this gives you a 20% reserve for the extreme weather, or about 4 8-10min cycles per hour and maintain a constant temperature with around a +or- 2deg variation. You shouldn’t need a dehumidifier the 3 ton AC is a dehumidifier though it will dehumidify with wiring change above. I have over 20 years in the HVAC trade before getting into the spray foam business and I still am learning about new problems when we create the climate isolation that we have been working so hard to achieve for so long. hope this helps thanks Airpro HVAC and Spray foam
Karli Pritchett Posted: May 17, 2010 07:28 PM	Thanks for all your help! Do you think the fresh air vent in combination with a central dehumidifier will do the job, or do you still suggest an HRV? If so, why the HRV instead of an ERV?
John Shockney Posted: May 18, 2010 12:01 AM	Depending on your location and climate you should not need a dehumidifier your AC should provide all the dehumidification that you need in the summer and during the winter if you have enough indoor to outdoor air exchange you still should not need a dehumidifier as long as the air outside has a low humidity. The choice of an ERV or HRV would be the manufactures recommendation for your climate check Fantech’s website at: http://www.fantech.net/hrv_erv.htm they have a good website that can help you with that choice. You can accomplish the same thing as a HRV or ERV with a fresh air vent although you will be dumping your heat (and $$$) to the outside; a HRV minimizes the lost heat (and $$$) by recovering the heat and warming the incoming air. Also check your furnace control board for a dehumid terminal and ask your HVAC contractor why it isn’t used. Hope this is helpful Airpro
mason Posted: May 18, 2010 07:46 AM	Airpro is giving good advice and information. I would defer to his experience as a HVAC contractor. As he suggests, it is important to obtain information from folks who are familiar with SPF and HVAC ventilation requirements. We have to remember that in this forum we can only provide so much detailed advice. Many cases require an analysis onsite by SPF experienced professionals. But if your local HVAC contractors are not familiar with working with SPF, then they should be informed that they cannot use the same calculation assumptions on SPF insulated homes as on conventionally insulated homes. For example, when I had my townhome sprayed with foam in Northern Virginia. After 2 years I replaced my furnace and AC. I told the HVAC contractor to recalculate his assumptions for the size of the units to account for the extra sealing benefits of the foam. As a result, we went from a 2.5 ton AC to a 2 ton AC and reduced the size of the furnace 2500 BTUs. My humidity level in the house tightened up from a previous 65% in summer and 15% in winter to no more than 55% in summer and 35% in winter. This is without adding any additional ventilation, ducts or make up air. As Airpro states, your AC unit must run consistently to take moisture out of the air
mason Posted: May 18, 2010 08:22 AM	I was re-reading your original post and had another observation. 1. Windows: I may agree with the advice on changing to vinyl from aluminum windows to reduce the potential for condensation. Aluminum is a good conductor and would be closer to the outside temperature than the rest of the wall assembly. This could cause condensation inside even if your humidity levels are fairly moderate. For example, at an interior temperature of 70 degrees F and a humidity of 50%, you would have a dewpoint of 50 degrees F. Even at 35% humidity(the lower end of the sweet spot for comfortable humidty) humidity, the dewpoint would be slightly above 40 degrees F. It is possible (depending on the window case construction) that the aluminum in winter would go below the dewpoint temperature on the inside causing condensation on the frame.
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: May 18, 2010 10:11 AM	SO, you have 1392 sqft of carpet with concrete under it and it can only dry to the inside?? I believe this is the problem! The carpet and carpet padding don't act as a moisture barrier and the moisture from the conrete can evaporate into the house. You don't notice it or feel it because it's much like a door wide open. The volume of air may be moving through the door but when you close it down to an inch open, you'll then feel it because of the velocity of the air. The vinyl/linoleum flooring can reduce the moisture penetration but the rest of the floor 1392 is open to air out - especially in the winter time when the house is closed up tight and the heat is on. Then on top of that, you have aluminum windows which can conduct the heat quicker, causing condensation on the bottom of the windows. The soultion is to reduce the amount of moisture coming up through this floor square footage by using a carpet pad that is also a vapor barrier or paint the floor under the carpet and padding to prevent moisture vapor from rising up through it. The product we use is called ThermE Pad and it's a carpet pad and a mositure vapor barrier all in one. Let us know how it works out. Jim
mason Posted: May 18, 2010 11:02 AM	Another thought. You mention that 3 HVAC contractors provided the same HVAC equipment and ventilation recommendations based on their manual j calculations. Ask them if their recommendations would be the same or different if using fiberglass or cellulose. The answer should be different. If it is the same, they are not taking into consideration the extra air sealing characteristics of the foam As you can see by the thoughts, analysis, observations and recommendations, that many things could be contributing to your problem. This reinforces the idea of having an SPF experienced HVAC or building science professional take a look at your situation
Karli Pritchett Posted: May 18, 2010 03:21 PM	FINALLY!!! You guys are great! Today's answers are really making sense to me. Let me add that my first expert was, in case you've heard of him, if not you can google him, was Richard L Rue. He lives about 3 hours from me and did all the work over the phone. He is what I consider an expert, just check out his credentials. I had him on the phone with my builders ac guy so he could tell him what needed to be done. First, he told the builder's ac guy to change my 3 ton unit from 20 killowatts to 10 killowatts, and to remove 2 heat strips? We are all electric. Second he said all windows should be changed from alluminum to vinyl and my problem would be solved. He also assured me that if my builder refused to make these changes(the windows) that he would be more than happy to go to court with me, he assured me they would not go against his suggestion because they did not want to go to court againt him. I informed my builder about his suggestion to change the windows, he was screaming mad, and refused. I still do not want to go to court, and when I got off the phone with him I started doing more research. I couldn't find anyone else to say foam houses REQUIRE alluminum windows. I also discovered that alluminum windows are stronger and maybe better than vinyl. I started to think my problem won't be solved by windows, I figured we needed to control the humidity level in the house first. In the meantime my builder called me to schedule a time to come install my new vinyl windows! I told him I was re thinking Richard's advise and he said good, I don't agree with him either! Apparently he figured Richard to be an expert he didn't want to question, or be sued by. He then told me Richard was nuts and his ac guy thought so as well because he only removed half of what Richard had told him to because he didn't agree with him. That kind of upset me that his ac guy who apparently had no knowledge or expertise in spray foam house ventilation decided to go against an obvious expert. That's when I decided to look for my own HVAC guy! So I had a local buisiness with a very good name here in east tx, that has been in the ac buisiness for many years come out to my house. He is the one that did the blower door test and suggested an ERV, and a central dehumidifier, all for ONLY, $9,250.00!! Again, my builder refused this proposal as well. My builder who has ABSOLUTELY no knowledge in ventilating a spray foam house is the one who suggested his guy could put in a fresh air vent for a couple hundred bucks if that's what I wanted, but threw up his hands and said I don't have a clue what will fix it!! Which leads me to where I am now, more research. So I guess my next question is, how do I know I'm getting an SPF experienced HVAC guy? They have all told me they are SPF experienced HVAC guys yet all disagree and have their own opinions. They don't have to be expeerienced to say they are right? And, how would I find a building science professional? Is he some one who would actually know and guarantee a solution?
John Shockney Posted: May 19, 2010 12:55 AM	It is a sad fact that it is really hard to find a good contractor most of them that have been in the business a long time got their license under a grandfather clause and didn’t have to show any training or take any tests. Others went to classes so they could just pass the test but don’t keep up with the new tech. And still others hire salesmen to sell expensive fixes that will work and if they don’t they made enough profit to cover their ass. I have 30 years in the HVAC and building trades mostly as a service tech fixing other peoples screw ups at times I found that the installers from the contractor that I was working for gave me job security due to their poor installations. It makes sense that you need to control the humidity in your house if your windows are sweating no matter what they are made of and yes vinyl or wood frames do have a higher insulation value and shouldn’t sweat as badly. 2nd it sounds like you have a 3ton heat-pump with a 20kw backup heat kit this does sound to be excessive but I don’t know your climate (I’m in Indiana) but if the system is setup with the proper controls (thermostat) the heat should come on in stages 1st the heat pump 2nd the electric backup and the electric should also come on in stages 5kw at a time. If setup correctly the blower in a system like this should run almost constantly in cold weather. And most of these systems have a dehumidification cycle built into the air handler requiring no modifications only some wiring and a new thermostat. Question, where is the air handler installed? Where is the ductwork? I do think the water is coming from the slab and will get better with time but I also know that doesn’t help right now. One fix would be a portable dehumidifier until the slab dries out. Call me if you need help getting the dehumidify cycle wired I can talk the tech through it 765-808-4262 Airpro
Karli Pritchett Posted: May 19, 2010 10:14 AM	It is sad that it's so hard to find a good contractor. What's even worse I think, is when you have builder who knows of at least 7 of his homes having the same problem, and he's not trying to figure out why or what he maybe did wrong so he doesn't do it again. If it was my buisiness, I'd be figuring out where I messed up and why, and making sure I fixed it and it never happened again. By the way, I am in east TX and our climate is hot and humid most of the time. Also, I checked on your fantech page yesterday and it is recommended we do have an erv, but it said when using erv's and the temp is below 23%F for more than two consecutive days, which it was here a few times this winter, to install a defrost option. Is this commmon knowledge? Also our air handler and duct work is in the roof (attic). Say the moisture is from the slab, there are spray foam houses all over built on a slab, and they don't have excessive moisture causing mold! So, don't you think, even if the moisture is from the slab, that they missed something, that if properly ventilated, there wouldn't be such a problem? Also, I reached expert #4 yesterday and he will be here Saturday to look at everything in detail, but his over the phone assesment was an erv.only. Out of curiosity I asked for a ball park figure on an erv and central dehumidifier and his price was around $5,000.00!! That's a lot cheaper that guy #3!! We have done the portable dehumidifier thing, and that's just not a long term or even month long fix for me! The noise and hassle of constantly dumping that thing, no, I did'nt build my new house to have to deal with that. Have you ever heard of my problem before? If so, do you know of anyone with my problem who has found a solution? If not, don't worry I'll keep you guys posted. Hopefully, I will find the fix, and when I do, I plan on spreading the word, so this doesn't happen again! I wish there were some rules and regulations for the spray foam installers, HVAC guys, and builders to have to follow, so spray foam houses could get a better name and better results!
Karli Pritchett Posted: May 19, 2010 10:14 AM
Robert Jordan Posted: May 19, 2010 02:58 PM	ASHRAE standards recommend 1/3 of an air change per hour or 8 air changes per day - which is what one contractor recommended to you. In winter an HRV or ERV exchanges the heat from the house with the incoming air so all the heat isn't lost. An ERV adds dehumidifcation to the ventilation aspect of the HRV. These are for indoor air quality, not necessarily for dehumidification, although it should help in the winter when the outside relative humidity is low. One thing people haven't pointed out is that a new house has a lot of moisture in it. From lumber that hasn't acclimatized to its final moisture content, as well as plaster and moisture in the concrete slab. Your second winter should be drier. I think this may be the cause as it doesn't make sense that the humidity is lower now than it was in the winter. You also need good bath fans and kitchen exhaust fans in a tight house. Most bath fans are junk and do not have the power to exhaust. They are tested and rated with 6 feet of straight duct. Every elbow in the duct reduces its effectiveness significantly. How about your dryer? Is it exhausted to the outside, again in a short run. I saw one house that had 60 feet of duct and 10 ninety degree elbows. It won't ever work. I would expect your AC should do a good job of dehumidifying. Unfortunately most systems are oversized in typical construction. If the same sizing method (usually a guess, not a load calculation) is used in a tight house the AC will be significantly oversized. The problem is the system is not on long enough for the AC to dehumidify the air.
Edward Brassington Posted: May 25, 2010 10:56 PM	What type of spray foam was used in your home. Was it open cell, if so was a vapour barrier installed. In your climate I believe the vapour barrier should be on the outside. If you have open cell foam and no vapour barrier it is possible that the humidity is entering through the walls and accumulating inside. Try to find an energy inspector that can test for moisture in the walls and other building materials. An Infra red scan may also point to areas of poor insulation and areas of air infiltration. An infra red scan done along with a blower door test may yield some surprising results. Also look at the moisture of the concrete slab. Concrete can actually take up to 7 years to fully cure. Perhaps a self adhesive vapour barrier over the concrete may help (concrete is not my area). Verify that all sources of moisture in the house are properly vented to the outside, washrooms, laundry, kitchen etc. Have someone measure the actual CFM discharge at each exhaust opening, compare that to the rated CFM of the appliance. It is possible exhaust ducts were damaged during installation. Good Luck.
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jun 01, 2010 07:48 AM	OK, enough of the Open cell absorbs water!!! All this does is confuse the industry and get us off track from what we should be doing which is beating up on the filterglass companies! Open cell or closed cell - foam is foam!!! They are both acting as an air barrier which blocks over 95% of the moisture transfer! So, how much more do you need to block? Little to none! An air barrier is the most important part of the moisture barrier needed! I know this is contrary to what some of the experts in the industry are saying but it is the truth! I've been spraying open and closed cell for years and haven't had an issue with mositure - even up in the Upstate NY climate!
Posted: Jun 09, 2010 06:52 PM	I was almost to tears reading the series of post discribing moisture problems and comments on the problem and solutions. My conclusion was that you can not kill an occupant with poor indoor air quality. So lets save energy and forget about the possible problems. I have had a change of heart. So hear goes, I feel sorry for you poor bastards. Tell me when you have had enough. Any occupied space should have and air change of clean fresh every 4-6 hours to purge indoor pollutants and renew oxygen. This amounts to about 60-100 cfm of fresh air when occupied. The heating, cooling, and dehumidifing cost is $200-300 per year. If that is too much for you, ingore my post. In green grass climate with below freezing winter temperature, the winter fresh air will keep the home dry enough to avoid serious window sweating during cold weather. Spring summer fall ventilation is a different problem. You need even more mechanical fresh air ventilation because of lack stack effect and less wind. The outdoor moisture content is higher and makes a home wet, therefore a good dehumidification system is needed to supplement the a/c in keeping the home <50%RH to avoid mold/mildew/dust mites and other biologicals. The simplest approach is a whole house ventilating dehumidifier which is capable of introducing fresh air when the home is occupied. They also maintain <50%RH regardless of the cooling load. The most concerning point is the total lack of understanding of this problem by the a/c contractors. The homeowner and builder depend totally on the a/c contractor who has no appreciation for the need of fresh air. People will be sich in these very well built homes. Get professional help from IAQ experts. Good Luck. Regards Grasshopper
Adam Beazley Posted: Oct 20, 2010 12:02 PM	This is something that happens quite frequently on spray foam homes, simply because the HVAC system is oversized. Generally builders will use their standard "rule of thumb" for sizing the HVAC system, which works just fine on a standard home with batt or blown in insulation, because it leaks, and the system will stay on long enough to dehumidify the house properly. In a spray foam house, there are no air leaks, so the house is super insulated and your conduction, convection and radiant heat exchange is virtually all but eliminated. So, what happens is the large oversized HVAC system kicks on, dumps a whole bunch of air (cool in the summer hot in the winter) and then shuts off. So it never gets a chance to properly dehumidify the the home and the energy bills are higher because the unit kicks on more frequently. Just get a dehumidifier for you home or downsize the HVAC system.
Adam Beazley Posted: Oct 20, 2010 02:45 PM	jimcooler, You do realize that an air barrier and a vapor barrier are two totally different things. Sometimes you want to use a vapor barrier and other times you need an air barrier which will allow moisture (vapor) to pass through. The wrong thing in the wrong spot in the wrong climate can and will cause condensation which will result in mold, rot, etc... We have seen many lawsuits as a result of improper installations.
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Oct 25, 2010 07:20 AM	Ys, I realize the diffeence. but if you have an air barrier, then you have most of a vapor retarder. This is because you don't have a cold surface in a warm moist environment (moist air). My questions was regarding the installtion of poly or a vapor retarder under the concrete floor, which s commonly missed and on the basement walls.
mason Posted: Oct 26, 2010 08:50 AM	Jim is correct, more than 90% of moisture comes into a building via air borne moisture. Separating the cold and warm side with effective insulation while providing an air barrier makes sprayfoam one of the better materials for controlling moisture. In cold climates the open cell foam needs an additional vapor retarder element since there is a constant vapor drive in one direction during much of the year.
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roger applewhite Posted: Feb 06, 2018 04:06 AM	Hi Karli; my wife and I live in Houston and are about to build a steel frame home. Like you, we want it to function as efficient as possible and were considering spray foam since it will be a metal building. However, my construction manager isn't big on spray foam due to the humidity levels here and how things can go wrong when there isn't enough ventilation. After reading your post, I see this is exactly what he is referring to. Did you ever find a fix/solution to your moisture/humidity issues? Any advice and/or information would be greatly appreciated. Thank you, Roger
Scott Lepore Posted: Jan 22, 2019 01:16 PM	Can anyone comment on the effectiveness of an ERV? I have the same problem as many of you do with the high humidity levels and I’m slowly trying to eliminate what I would guess to be individual sources of humidity - I just installed a gnarly bathroom vent and I’m on my way towards more effective kitchen ventilation. But until then I wanted to toss some ideas back and forth with everyone.