https://techxplore.com/news/2024-12-nondestructive-microwave-radar-moisture-walls.html
For homeowners, moisture buildup can cause the biggest headaches. Mold grows on drywall and wood-based materials, creeping along walls, floors and ceilings. Building materials begin to erode and rot. As insulation becomes damaged, the home's energy-efficiency decreases. Even human health suffers, as moisture also leads to air-quality issues.
The key to preventing extensive moisture damage is discovering it early, when it can be easily fixed.
Researchers at the Department of Energy's Oak Ridge National Laboratory are using microwave radar reflection to nondestructively detect and measure the moisture content of materials within walls without removing drywall or cladding. This also expedites moisture identification and enables mold growth to be treated in the early stages.
The research team's study results were published in IEEE Xplore and presented during the IEEE Radar Conference 2024 in Denver.
"We know microwave radar shows great promise for this, because it's well known that it can measure the moisture in wood samples," ORNL's Philip Boudreaux said. "But can it measure moisture in wood that is inside a wall to detect high-moisture issues before they become a big problem? That's the challenge."
The envelope of a building consists of exterior walls, the roof and foundation, all of which join to prevent moisture transmission. But the envelope is itself prone to moisture issues caused by many factors: too much rain, ground dampness, air leaking through holes, and vapor diffusion when moisture moves from higher to lower concentrations through the envelope.
Most homes are made from wood-frame construction, and when wood is moist, it's the perfect environment for mold to grow. If a wall is damaged or designed incorrectly, water vapor that seeps through wood can make it damp. For this reason, Boudreaux said, wood was selected as the initial material to investigate the capabilities of microwave radar.
"You can detect water within wood with microwave energy that reflects off of the material using radar," Boudreaux said. "You can also measure moisture in more than one type of material within the wall."
As part of the electromagnetic spectrum, microwaves interact with materials in a similar way to visible light, but they penetrate further, creating reflections. Radar systems work by emitting signals like microwaves and then detecting the reflections of those microwaves. When used with walls, the microwave reflection pulse characteristics are based on the moisture in the material.
Walls are made up of layers of materials, and each layer may have different amounts of moisture. However, by measuring the length of time taken for the microwaves to return to the sensor, the distance to each material in the wall can be calculated, and this can be used to map out and measure the moisture within the layers.
Journal Reference: S. Killough, P. Boudreaux and R. Zhang, "Measuring the Moisture Content of Wood Sheathing with Continuous Wave Radars," 2024 IEEE Radar Conference (RadarConf24), Denver, CO, USA, 2024, pp. 1-6, doi: 10.1109/RadarConf2458775.2024.10548546.
(Score: 2, Interesting) by Anonymous Coward on Thursday December 26, @01:13PM (5 children)
In the '70s I took a building technology class. At that time the recommendation was for vapor barrier on the inside, in northern climates where heating dominates. A typical problem is that people like electrical outlets on all the walls (outside as well as inside walls). Unless carefully taped up before sheet rock is installed, the leaky electric boxes let moisture into the outside wall cavity, mostly in kitchens and bathrooms (the high moisture parts of the house).
Assuming everything is porous to moisture outside the vapor barrier, the moisture migrates out to the cold/dry outside air...unless it's cold enough that the temp is below freezing someplace in the middle of porous insulation (fiberglass), in which case it frosts and reduces the insulation R-value of the wall...
In recent years, when I see new houses going up, they also have an external vapor barrier under the outside sheathing, and this may even be required by code(?), since it seems to be universal. From my simple understanding, this seems like a recipe for mold, since any moisture that leaks into the wall from the inside can't get out (unless the external vapor barrier is poorly sealed at the same stud spaces where the inside leaks are located...)
Note that in climates that mostly air condition, then the high humidity is often on the outside (think Florida) and there it might make sense to put the vapor barrier on the outside. I'm from the north, do Florida building codes require this?
Where is Mike Holmes to explain all this (for cold climates)?
(Score: 2) by JoeMerchant on Thursday December 26, @09:03PM (4 children)
Cynically, mold is a driver of remediation and remodeling work, so of course builders are onboard with energy efficiency codes that might increase the incidence of mold.
Warning: nothing is logical in the following anecdote.
Friends of ours were in the middle of a roof replacement when a hurricane struck and put water down into their walls. The two adults and two highschool aged kids moved down the street into two adjoining hotel rooms in October and aren't expecting to move back into their house until February or later. The remediation company might start work next week. Meanwhile they have been shuffling possessions out to various storage locations, cleaning what they can along the way.
I loaned them an industrial strength ozone generator when I thought of it in December, apparently that's pretty effective for the surface smells, but it goes deeper.
Return of logic:
When I was considering a move to Hawaii, practical single wall construction was one of the big appeals to me.
🌻🌻🌻 [google.com]
(Score: 0) by Anonymous Coward on Friday December 27, @12:05AM (1 child)
> ... considering a move to Hawaii, practical single wall construction ...
Have been to Hawaii a couple of times (Oahu & Big Island near Hilo/rain forest) Don't recall hearing anything about single wall homes, I was probably in newer areas. This gives an overview,
https://www.signatureinspectionshawaii.com/ask-the-inspector/q-a/difference-single-wall-double-wall-construction/ [signatureinspectionshawaii.com]
Link mentions air conditioning being easier with an insulated house (true), but doesn't mention the big hitter--the cost of electricity in Hawaii is 1.5-3x higher than continental US.
(Score: 2) by JoeMerchant on Friday December 27, @02:11PM
So, the reason single wall works in Hawaii, particularly at certain elevations, is that the climate is relatively constant year round.
Even if you want a little A/C, the heat differential is low, so insulation isn't as important. And while electricity is expensive, PV solar is about the same there as anywhere, a little better if you are in a low cloud cover part of the island.
🌻🌻🌻 [google.com]
(Score: 2) by driverless on Friday December 27, @09:15AM (1 child)
Warning: nothing is logical in the following anecdote.
Friends of ours were in the middle of a roof replacement when a hurricane struck and dropped a house on their neighbour who was widely rumoured to be a witch. They sold some sort of red shoes they wound on the corpse to pay for the repairs but wound up in debt to a Hutt who forced them to mortgage their Aluminiun Falcon to pay off the rest of the debt, but a Klingon Bird of Prey decloaked and de-rezzed it before they could deliver it to the pawnbroker.
Return of logic:
There are a lot of chemicals in the water here I live.
(Score: 2) by JoeMerchant on Friday December 27, @02:15PM
The illogical family is our son's girlfriend's.
We can't plan anything with them more than 24 hours in advance (usually more like 3), because the chaos erases all structure that far away in time.
🌻🌻🌻 [google.com]
(Score: 2, Interesting) by SnorkleZ on Friday December 27, @03:20AM
Moisture infiltration is a huge problem for sailboats. Something better than the existing capacitance-based testers or the "it feels pretty spongy to me" test would make used boat buying a lot less stressful.
(Score: 2) by driverless on Friday December 27, @09:10AM
"National lab comes up with complex, exotic, and expensive way to play with microwaves, invents something for it to do, and hopes no-one remembers you can buy pinless moisture meters that do the same thing at Walmart".