Great information as always

Great video with data-based discussion. In my opinion, this study needs to be updated to represented three factors that have or are becoming more common in build methods. One factor is the air and water sealing apply to external sheathing. During the time of this study, air sealing the sheathing was an uncommon practice. The second factor is the house sheathing standards are beginning to require foam insulation backing. In the North Carolina region, R5 sheathing is slowly becoming adopted to new builds and complete rebuilds. The third factor is time. This study represents one year. It would be a more complete picture if this was a 10 or 15 year study. Fiberglass in an open cross space does not have the same insulation value at year one compared to year ten.

Great food for thought for my new build in the VA mountains. Much appreciated!

This is very helpful! Thanks great. Have a good long weekend!

Good report Michael! Good data for mid South applications.

This result makes sense. For the first year, the house with insulated crawlspace walls and no insulation to the floor is effectively making the entire crawlspace floor as a thermal mass, which helps regulate the temperature. At first, the crawlspace ground will be colder than room temperature, so it will help with cooling and hurt heating. Over time, the crawlspace ground will become closer to room temperature and be less of an effect. Even with these results, encapsulating the crawlspace is way better in the initial cost, short term, and long term.

First I want to thank Crawlspace Ninja, especially Michael for introducing me to Crawlspace Encapsulation. Before encapsulating my crawlspace we had a lot of moisture problems, leading to mold on the joists. As well as having rotted sill plates in areas, as well as band board. My son was diagnosed with Beckwith-Wiedemann syndrome just before his birth. This syndrome though it is very mild in consideration to others out there, can contribute to breathing difficulties. (Which he had) and after stumbling across this channel, and hearing about all the benefits that it can do as far as cleaner breathing air in the home, my wife and I made the decision to hire a contractor as CSN wasn’t available in my area. When I hired them they had their own way of doing things. But after hearing from what I had to say as far as how you guys do it. They modified their procedure to the way I wanted it done. And long story short, my son is no longer on oxygen. His coughing has tremendously improved. And he is nine months old now and doing well! So thank you very much for making these videos! Sorry for getting a bit off topic there. But one question I have (My encapsulation was done with foam walls no subfloor insulation.) Do you know if the duct system was ran in the Crawlspace in these homes or did they run in the attic? Out of curiosity, if they were ran in the Crawlspace would that have helped with energy consumption in the winter time as it would have helped heat the Crawlspace and retain heat? Thanks again!

Great video. Definitely learned a lot

Thank you for the information I'm about to start my crawl space project I will get back with you on how it went. Boy do I hope it goes well.

Thank you for sharing that data and for being honest about encapsulation. Most companies doing C.S. encapsulation are intentionally misleading or they price gouge the homeowner. i just wish Crawl Space Ninja was in Southern West Virginia. Great video!

Great video

Another thought too, is wind averages for the site of each of the house. Some homes placement results in passive solar gains/loses. Just as wind can create some really strange heat losses/gains. But each home is different, and this is why you should thoroughly investigate all options to maximize your energy savings.

The testing occurred in Princeville , NC which had been nearly completely destroyed by Hurricane Floyd. In some places, original homes there were inundated by upwards of 30 ft of flood waters after a major failure of the levee system there. Hence the ability to have all these identical houses in one distinct area.

Thank you

I live in Virginia and after doing research, I decided to go against the grain. I am putting borafoam on my walls in my crawlspace, but I am also putting R38 fiberglass insulation back in the joist as well. After watching this video, it seems the way I went was the best way to go. I am doing the work myself, so its only the cost of materials. I went with the R38, because when I purchased it, it was cheaper than R30. I know its an overkill, but its my money and my time. I am also putting 20 mil vapor barrier down as well. All in all, I will get my investment back long term in energy savings.

Hello everyone, I have published a book, "Crawl Space Repair Myths-Busted: Avoid Bad Advice, Bad Decisions, & Bad Repairs" on Amazon if you'd like to check it out. amzn.to/3Hhy4lL

Pretty interesting, I honestly would have figured the savings to be higher for either over control. After the cost of materials and labor that is a huge time frame for ROI. It seems to me though, the ideal situation would be to have both wall and floor, but in the summer use adjustable baffles/dampers to divert your source of return air to be from the basement/crawlspace so you can take advantage of that cool earthen air. Not sure if you'd want to have that basement/crawlspace air supplemented with a dehumidifier. Once you start dehumidifying that adds a whole other variable.

Metro Detroit here - non-scientific data point for you. I purchased my 1960-built house in 2018, it had the plain vented crawlspace (about 432 sqft) with subfloor insulation (I don’t remember the R value) and a vapor barrier on the dirt floor. 4-foot concrete walls on the exterior three sides; entry is from inside the house. My biggest worry was the pipes freezing in winter; on the coldest day of the year in Jan/Feb 2019 when it was around -11 F, the kitchen faucet pipes froze for a few days but thankfully didn’t burst. I put a wifi thermometer/humidity sensor in the crawlspace just below the faucet, at least to be able to watch it. Later that year I hired a company to encapsulate (this was before I found your channel). They took out the old vapor barrier and insulation, installed a new thicker vapor barrier, 2-inch rigid XPS foam insulation on the exterior walls, and vapor barrier with tape sealing over that. They also put fiberglass into the cavities in the rim joists. Later on a friend’s advice I cut up some of the leftover foam to block the vents from the inside. All that together seems to have helped to keep the crawlspace from going below freezing. I’ve not had my pipes freeze since then; today was single-digit weather but my sensor shows that the temp inside the crawlspace only dropped from 53 to 47 degrees over an 11-hour period. The floors above are still cold, but I have little to no fear anymore of the pipes freezing. And it’s very dry in winter, usually in the 25-35% range. I was even able to close the baffles on the ducts that open into the crawlspace (but they’re old so some air still gets out). In summer it does still get very humid; I have a dehumidifier with a pump and drain tube leading through the interior wall into the utility room drain. I also experimented with using a crawlspace vent fan in the summer; it helped but wasn’t as effective in high humidity periods. So I’m basically Team Wall Insulation after all of that. I did start noticing a year or two ago that after it snows, an area of the concrete extending about 2-3 feet from the house seems to clear on its own. That tells me some heat is still getting out , most likely through the sill joists. I’m wondering about going back in and replacing (or adding to?) the fiberglass batt insulation with the rigid foam in each cavity, either pressed tightly into place, or maybe loose fit and then sealed with caulk or Great Stuff around the edges (I’d seen that on a different channel).

I had my 2700 sq. ft home encapsulated in 2019 immediately after I bought it and both my wife and I noticed how cold the house felt in the winter. I wished I had waited and compared my first year in the home with the R-19 fiberglass insulation to after encapsulation. I had full trust in Crawl Space Ninja so I put my "winter cold home" thinking to rest, assured that my wall insulation was best. Well!? . . . this video seems to validate my winter/colder floor previous thinking. I'm in Western N.C. and it just got down to 8 degrees with a minus zero wind chill. It can get cold in the Carolinas. Wonder about some foam board in-between the floor joists, or even a lesser R rated/cheaper fiberglass insulation.

Another factor to consider in colder climate areas, is that the frost line is much deeper. I live and build in NC now but lived most of my life in VT. A crawl space in places like VT would be at least 4' in the ground and with ground adding a insulating factor wall insulation would be much better choice.

good job.

So… floor joist insulation for Winter energy savings…and foundation wall insulation for Summer energy savings?

I live in Northern IL winters here can be rough

I’d love to see an updated study with the latest technology (insulation, ventilation, foundation materials).

Interesting. As a newbie to the topic, it would have been most helpful for you to show images (or even a better a video) of each of the three options.

So probably makes sense if you are in the 4A or 5A areas of the energy star chart should probably do both. I had bad floor insulation that needs replaced and was going to put in R30, but I think the R19 (which is recommended here in 4A in Maryland) with the wall insulation should do best.

So in the northeast, this house in this crawl space has a vapor barrier, insulated foundation walls with 2” reflective foam board in a sealed space no humidifier or vents (at the moment). Also it has heat/ac duct going to a floor register above and water lines for stacked washer & dryer; would you recommend insulating the floor joists? Cold floors stink in the winter here in the northeast. What do you recommend ninja? 👍🏻

Curious to know if the performance would favor sealed with wall insulation in winter months with humidity control

I live in tulsa oklahoma. I put reinforced vapor barrier on floor and walls like you teach. I insulated rim joists with foam board and sealed with great stuff then put rock wool over the foam board. Should I do the wall insulation and also floor insulation in oklahoma?

How do you deal with the code requirements related to fire barriers? All building code I have seen requires a fire barrier on the rigid foam that would general be installed on the walls.

Thanks for the video. Very informative video. I'm struggling in getting data on if I should upgrade my insulation in my ~23 yr home in NC? Ventilated crawlspace (1st floor ~2500 sq ft) floor joists 2x10 16 OC insulated with R19. Insulation is showing its age and was not sure if there would be any ROI with replacing/upgrading floor insulation.

So my home has subfloor insulation already. We live in VA. I can't decide if I want to insulate the foundation wall or just encapsulate without wall insulation.

A problem that might happen if you put down a vapor barrier on the ground of a crawl space is if you had pipe burst it might cause a problem if the water couldn't drain into the ground.

I'm guessing the sealed houses with wall insulation were not a conditioned crawl spaces? if not it would be cool to see that one added to the study.

If I close up an open crawl space in Cincinnati and decide to go with insulating the wall, should I seal and insulate the rim joist as well?

We bought a used home in Texas. Built in 1952, we put insulation in the attic and the outer walls, We’re on pier beam. It’s vented with no insulation under floor. What should I do. Floor is cold in winter even with carpet. But feels good during the summer. Any recommendations?

Either way, looks like the best practice is to wait until April to install wall insulation, and ride out the winter with just floor insulation in place.

I have a quick question. I live in AZ and we are building a cabin in the white mountains. 6,000 feet elevation. Summers are pretty mild (we are not putting in central air) and winters can get down to 0* F. We have a crawl space with a vented stem wall. My main concern is pipes freezing during the 2ish or less months that it does drop below 32 at night. Our plumber recommended not insulating the floor so the ambient heat from the house would keep the pipes from freezing. Would using wall insulation help with that. We've been getting estimates and all of them want to spray foam the sub floor. Thanks.

I have a side room on my house. The attic could use more insulation but the floor in the crawlspace has none. I'm on a limited budget which should I do first to keep the room warmer (add more in the attic or insulate the floor)?

I'd be curious to see what type of flooring they had on the interior of the house. We found that hardwood floors and tile houses benefit from subfloor insulation more than you would expect. Our best guess (no study commissioned) from conversations with home owners is because people don't like their feet to be cold in the winter. If the floor is cold they crank up the heat. But in the summer they don't crank down the AC to make the floor cold. I have a friend in Tennessee on a farm, he cringes every time his wife and daughter turn on the heated floor in their bathroom. Especially in the summer when the AC is set so cold they have to run the floor warmers! ; )

Do the energy savings related to sealed crawls in the study take into account the energy used by dehumidifiers in the sealed crawls?

Cooool!

I recenally had my crawl space ecasulated with a dehumidifer and sump pump. However I don't have any insulatoion. They said it is best to leave one vent open for ventlation. Is that correct or should I close off the last vent? Also do you know how much I'd save by adding insulation to the walls right now it is just the poly on the walls. I am in Georgia if that helps.

Very interesting video man thank you for the information. I submitted a form on your site I would like to talk to you about a crawl space I’m building soon

Should you take down existing R-19 fiberglass batts in subfloor or just leave them in place? I plan on doing 2” foam board insulation to rim joist and block wall. That is also along with E80 Aprilaire and foundation vent fan.

could the difference in winter saving for r19 be better because the floor insulation would partially help seal that critical rim joist area whereas the ridgid foam would not cover that area at all. I would be interested to see if that study included a rim joist insulation or if r13 wall insulation with rim joist air seal outperforms in all climates.

Bought a manufactured home last year, finally ripped out the carpet in the living room and replaced it with a vinyl floating floor and under that a very thick quiet mat moisture barrier. Once summer hit the subfloor under the vinyl has started warping. o_0 I am assuming the vapors can no longer escape due to the moisture barrier and is causing water damage on the subfloor causing it to warp. Before I replace the subfloor I need to figure out how to stop this from happening again... I am hoping just removing the moisture barrier under the vinyl floor will stop it... but idk.

With our new build home here in Clarksville, it has subfloor insulation. If i understand you correctly, we would benefit from wall insulation. Plz advise.

Crawlspace Ninja: I am encapsulating my Crawlspace, in climate zone 5. Do you think i still need insulated ducts or can i safely use standard flex duct?

Ever used this product? SmartSHIELD -5mm 48"x50ft Reflective Foam Core Insulation roll, Cold and Heat Shield, Radiant Barrier, Thermal Insulation - Engineered FOIL / White Film

Hello Crawl Space Ninja. We're in the great cold State of Michigan and is highly considering insulating our roughly 500 sq ft addition/room on the rear of the home. It sits above a nearly 3 ft high uncovered dirt crawl space with two vents. No other insulation exists, nor does pipes exist here. This room offers freezing cold in the winter months. Now, there's 1 heat register, but of course, this room isn't containing heat. For clarification, would using closed cell spray foam (or) 2" inch foam board reflective insulation be useful with adding insulation to the floors boards with R-19 rolls?

I live in NC. So can I use wall and subfloor insulation?

So every home had identical HVAC systems and identical floor plan. Additionally did they monitor the thermostat settings for each home

Where can I send my pics I’m ha just finished my removal of fiber bats that the installer did paper side down lol in 1980.

So if I'm thinking of encapsulation, shouldn't I leave the fiberglass floor insulation?

I'm in Michigan and going to try the wall insulation... see what happens

The sun's effect on heating and cooling costs as related to wall insulation will be affected by a house's eves and the angle of the sun to the wall and the eves. Further, as the wall is heated this way, so will be the crawl space, and so the need for floor insulation.

Based on this study, in general, north of the Mason Dixon line wall insulation would be king because of the super hot summer temperatures. In the North, subfloor insulation would win because of the really cold winters.

had a thought to use a smart vapor retarder on the underside of joists to further reduce humidity that hits the framing. on top of vapor barrier on the floor and powered exhaust vents in the wall. any thoughts on this? currently putting down your vapor barrier in the crawlspace

The big unanswered question is *why* did floor insulation-only perform better than wall insulation during the coldest winter months in this study, and was there something specific and unusual about the homes in this study, or can this unexpected result be generalized to any home.

I "suspect" the energy improvement for vented crawl spaces during November, December, and February was due to the crawl space acting as a thermal energy battery-thermal energy is being stored in the floor of the crawl space during October. So why was January worse, because “likely” the thermal energy improvement is related to rate of change towards cold weather. So, does anyone sale an insulated basement vents and controller that I can open in October and when the outside temp is above a fixed temperature. (like above 72F in November, December, February, plus below 75F in July, Aug, etc)? I need four vents and a controller. P.S. I already use part of this strategy in my attic with a humidity sensor so I’m not letting too much moisture into my attic - same humidity sensor concept would apply to crawl spaces.

If a company as yours bids on a crawlspace job which is determined to be extensive, and the crawlspace height is 4' at most, do your workers approach the space from the crawl opening at the foundation, or cut openings into the subflooring from above? How would you pros decide? *And again, Oregon is starving for such a service.

I am glad they at least pushed to run the study 12 months of the year anything less would have been pointless. What disappoints me about the study is that there were too few homes with unaccounted variables. It sounds like this study only looked at overall energy usage, not necessarily the type of energy used or how. 1. What was the preferred thermostat setting in each home? 2. Was the HVAC on a schedule or always on? 3. Were the windows always closed? 4. How often did the residents open or enter their crawlspace? 4. Were the residents keeping up with their air HVAC filters? 5. Did anyone set up Holiday Lights and was that lighting usage comparable (Pre-LED that made a huge difference)? 6. What was the age of the HVAC system? 7. Did they all have the same HVAC system? 8. Did they have guests or residents who just left lights/fans/space heaters running for personal comfort? 9. There was not have a home with sealed vents that insulated both the subfloor and crawlspace walls (Maybe we get 21% savings). 10. There was not a control with no insulation at all. 11. Was the actual ground in the crawlspace lined with vapor barrier or, was it bare? 12. If the crawlspace ground was bare, was there a difference in elevation and ground moisture?

Sounded like repetitive humidity played a role here, but the data talks about pure energy use in units.

did all these people keep the thermostat the same?

How about basements? Northeast.

Did they install a dehumidifier and insulate the rim joists for the study? Surely someone online can provide data from their encapsulation results over a period of 2-3 years. I would think Crawl Space Ninja would have paid someone to provide data...

Our crawlspace is open

Actually, logical. The crawl space is a heat sink. In the summer, it actually acts as geothermal cooling for the house. The more effective insulation actually works against you in the summer because you lose the cooling effect of the ground beneath the house. The more effective insulation is subfloor because it actually is a barrier to the cooler crawl space. But, in the summer in a hot climate, you don't want the more effective insulation because you want to leverage the cooling effect of the crawl space. Maybe the answer is to seal the crawl space, insulate the walls, and open a vent to blow some heat into the crawl space - lotta work. Maybe the simple fix is to insulate walls in hot climates and floor in cold climates. However, the other wild card is the hours during the day power is used and the affect of teired rates based on peak demand hours. This could really skew the results of this study which only considers actually power used and not "the bottom line" - that would be cost. In the winter, more power usage is in the evenings and at night, which is generally at a lower rate. In the summer, more power is used during the day and is at a higher rate. So, it may be best, in all instances, to insulate just the walls based on cost. Or, in the case of my cabin, only the floors because I don't cool my cabin in the summer because the ambient temp hardly ever gets to 90, but it gets to zero in the winter.

I want to start insulating my crawl space but it has been raining quite a bit. Should i be concerned about the possibility of trapping moisture (from maybe accidentally getting my foam wet) in-between joist and foam??

I bet if the R-13 wall insulation had been R-18 instead, it would have done better than floor R-18.

FYI, you don't need their permission to share information from this study, or from anywhere.

In other words the energy savings with the sealed crawl space will never be able justify the cost of sealing the crawl space.

Definitely not a large data set. If a couple of houses in any of the three sets of four houses used in the study kept their thermostats higher than average in the winter or colder than average in the summer, could definitely skew the results.

Have to be suspect about a report 18 yrs, Do this report again with new building products and techniques also it should be regional only

This study forgets spray foam…. :(

Ah I think your interpretation of the data during the colder months is wrong. There’s essentially no difference between all of them. The error bars overlap each other essentially every single case. There’s no statistical difference.