Dehumidifier for forced hot water by oil heater

barbarapratt

My son recently bought a house (built in 2003) with heat by forced hot water by oil. It has baseboard heating fixtures. The place is like a sweatlodge! It is 2 stories plus a garage under. It's about 1500 sf. Its not that it is extremely hot but it is extremely humid. He lives in the NE USA. They are beginning to have mold problems. Is it possible to install a whole house dehumidifier on a system like this?

don_9

First off let me say that your heating system has nothing to do with your mold issue unless it is leaking some where that you dont know about.If anything your heat plant should be lowering the humidity, bc of the air is expanding causing the number of grains of water vapor to occupy a larger volume of air.I can only assume that your son envelope is very tight which mean not only does he have a need for a dehumidifider but maybe some fresh outside air to lower the co2 in the home.Do a search on santa fe dehumidifiders.Go to their site and do some research it should help you with dealing with your son issue.

icesailor

More than likely, he needs an inside/outside air exchanger for winter time use. Cold air will carry less moisture than warmer air. Believe it or not, you can use "Mini-Split" air conditioners as whole house humidifiers to remove excess humidity because heat flows to cold, and dampness flows to dryness.

I think that Massachusetts Building Codes require air to air exchangers in new buildings. Not being enforced. They exchange warm moist air for cold dryer air and extract the heat from the exhausting air and add the heat to the incoming air.

You really need to get rid of that warm moist air. It will promote mold growth. If there is a finished basement, look in corners, especially outside corners near the floor and look for black spots or mold growth where a cold outside foundation is transferring cold and the warm moist air are meeting the Dew Point and causing condensation. Mold loves acrylic paint and Gypsum in wall board. Especially, look in bathrooms. Mold is really bad.

On Martha's Vineyard, they built a tribal housing project for the Gay Head Indians. The buildings were so tight and energy efficient that mold destroyed the places and made them unlivable before they moved into the last units. That's why AC is becoming more and more important in New England in the Summer. To stop mold growth and rot.

Mini-Splits are a wonderful thing.

John Mills_5

Is the humidity an issue in the summer or winter?

barbarapratt

I know it's a problem in the winter. Not sure about the summer yet, but I think so.

John Mills_5

One thing to consider is a whole house ventilating dehumidifier. It will dry the house year round. Even if you have A/C, there are a lot of times it is humid but not warm enough to have the A/C run enough to keep humidity under control. And you certainly don't run the A/C in the winter. The ERV/HRV works in the winter by bringing in outside air and recovering heat from the exhausting air but won't help humidity control beyond cold weather. The dehumidifier will lower the humidity year round. Many have the capability of a damper that opens usually timed to bring in fresh outside air and have it dehumidified before put into the house.

http://www.forwardthinking.honeywell.com/related_links/dehumidification/50-1018.pdf

ChasMan

In my case, dehumidifying in the summer fixed the issue year round since the house wasn't soaking wet when the cold air hits. I just use one of those huge Santa Fe units in the basement. Located in Danbury. I have an oversized ac so it didn't help much. The dehumidifier in the basement is set to 45%. Gets to 55 on the upper levels. In the winter it can drop to 25. Used to be wet year round. Wood holds a lot of water. That water took all winter to dry up before.

bio_guy

Are there exhaust fans in the baths and kitchen? If so, are they used appropriately? Is the foundation damp? Is laundry being line dried indoors?

Icesailor, minisplits and other variable-speed cooling is much better at humidity control than more old-fashioned slam-bang cooling, but it is no substitute for a dedicated dehumidifier in my experience. I always run a dehumidifier in times of high humidity when there is little need for heating or cooling. The mini splits still cool significantly in dehumidify mode. Sometimes I'll run one mini split in the house with the dehumidifier running or it gets too warm, sometimes not.

barbarapratt

Yes, exhaust fans are present and being used. Foundation is damp. They live in a pine forest. No line dryer. Clothes dryer is vented to the outside. I'm sorry, I don't know what a mini split is. Can you explain?

SWEI

Search for 'ductless mini split' and you'll see an entire range of options. They are by far the most common systems in much of the world.

barbarapratt

OK, good idea.

icesailor

@bio_guy:

bio_guy said:

Are there exhaust fans in the baths and kitchen? If so, are they used appropriately? Is the foundation damp? Is laundry being line dried indoors?

Icesailor, minisplits and other variable-speed cooling is much better at humidity control than more old-fashioned slam-bang cooling, but it is no substitute for a dedicated dehumidifier in my experience. I always run a dehumidifier in times of high humidity when there is little need for heating or cooling. The mini splits still cool significantly in dehumidify mode. Sometimes I'll run one mini split in the house with the dehumidifier running or it gets too warm, sometimes not.

That's true what you say. But I lived in a place at the ocean where it wasn't that hot but the humidity would kill you. People moved into their cellars and rented out the upstairs, or rented the cellars. At a 70 degree OAT, and a 70 degree dewpoint, a cellar is unlivable. So, they get some type of de-humidifier and pump the waste water into another place, maybe a dirt floor. But the waste heat for compression made the room even hotter. So they let the cooler moist air in. You understand the issue?

I did a brand new house with radiant in the ceilings. No AC. The two boys lived in the cellar. They would come home late at night and the finished basement was so hot that they opened all the large windows. A large puddle of water appeared. They insisted that there was a water leak in the ceiling. The closest water was 20' away. With the window open at night, the cool moisture laden air came through the open window and down the outside stairway, hit the cool tile floor, and condensed into water. I convinced them to put in a Mini-Split because a throw away dehumidifier would give off so much heat that the room would be hot, and they would open the door and windows again. I installed the Mini-Split and that was the end of that.

I don't make this ship up. I lived it. This place (heatinghelp.com) makes me remember so many crazy things I have been in to. If there's a problem, someone has to fix it. It might as well be me so I can learn something.

barbarapratt

He lives right on the Cape Cod Canal so your story sounds just like his house. I'm going to check this mini split thingie out and get someone to install one. Plumber? Electrician? HVAC person?

SWEI

HVAC person, but not just any HVAC person. You want someone factory trained on the specific brand and model line you specify. Lineset purging, evacuation, and charging are critical on these newer systems, and the controls are all different.

barbarapratt

OK, thank you so very much.

billtwocase

I live close to the Canal, and run a dehumidifier year round, Way of life near the water

bio_guy

Icesailor, "...You understand the issue? "

Yes, I understand perfectly. What I am saying is that my Mitsubishi mini splits have a dehumidify mode*, but it also cools. At 70/70, the house will get too cool. Sure, it is heavily biased to dehumidify, but the air coming out is cooler than that going in. If the house is on the cool side and humid, it will make it too cold all by itself. That is where the dehumidifier comes in. I am not giving mine up. In cool, humid times, I run the dehumidifier all by itself. In warm, humid , not hot times (70/70) , I might run both. If it is hot, just the mini splits run. Many periods in the spring and Fall, the dehumidifier goes on at night and the mini splits dehumidify in the daytime.

*I assume that this mode is similar to running on cool with the blower at its lowest setting yielding a very cold coil with low air flow.

bio_guy

Barbarapratt, I am sorry that we are getting kind of far from your problem.

A mini split is not what you want to do if you are humid in the heating season in what I would call the NE. A house normally ranges from dry to too dry under those conditions. I am working with limited information, but I feel that something is wrong with that house. (What are the indoor and outdoor temperature and humidity levels or what is the climate like where the house is?) In cold weather a dehumidifier is a better bandaid than a mini split. Note that any HVAC solution to this problem is probably a bandaid so if you are going to get a dehumidifier, an inexpensive one would be a better choice for a short term while you are figuring out what is really wrong.

I think that you need to have your house evaluated by an expert to find out where the humidity is coming from. That damp foundation is a prime suspect. If the soil around the foundation is water-logged, I hope that it can be trenched and tiling an pipes set up to drain it. Moisture proofing and sump pumps on the inside are not as good an approach, but might work.

Again, find an expert to help you figure out how to dry your house. High humidity levels will damage the house and can damage your health as fungus levels grow. In the meantime, get a couple of inexpensive electronic hygrometers, check them against each other and then start monitoring the relative humidity levels in the house and report back here.

barbarapratt

What would "an expert" be called? How would I find one? What questions should I ask?

bio_guy

You might start with your local home inspectors. I'd start with the largest ones that have both engineers and energy experts on staff. The bigger they are, the more likely they will have a person with specialized knowledge needed to figure out the problem. Call a number and interview them over the phone to see how they respond to the issue before you hire one. I'd start with some real data from the house. How humid is it? You'll go nowhere without defining the problem.

barbarapratt

OK, it looks like this will be a long term problem. We need hygrometers first. My son had a home inspection before he bought the house. What a farce. I guess I'll do some research for a larger company. Thank you so much for all the help.

don_9

Not only do you look at the inside of the building envelope you also look at the outside as well.we have lots of crawls in my area where drainage going away from the home as been screwed up do to all the high flower beds around the home.that water puddles then head down hill into the crawl.off topic,went to a home last week the guy was doing some work in the home.had all the windows open and a torpedo heater going.all the walls inside the home were sweating n beads of water running down them.hmmm who were have thought that would happen.lol

icesailor

Sorry folks. Some of you who do not live there, have no idea of the environmental conditions with temperature and humidity on Cape Cod, the Islands, and right along the New England Coast where the prevailing winds bring us that nice unregulated air pollution from Midwest Power plants and factories.

If you haven't seen the aftereffects of leaving a South, South West or West facing window for ventilation in July and August, and noticed that mold had grown in the wall around and under the window, you don't live near there. That Ethanol feeding black mold is everywhere. And there's that Dew Point thingy. Where the temperature and the dew point coincide to make the moisture drop out of water vapor. You can go down into a cool cellar for a while, but the humidity is 100%/ saturated and the dew point is catching up. In the corners of finished basements, there will be mold growing in corners. The black stuff. Sometimes you can smell it. Standard dehumidifiers generate HEAT to work. When you are trying to remove moisture/humidity with a dehumidifier, the by-product is heat. You will need AC to get the temperature down.

A "Home Inspector"? Like the one I met who told me that cold flows to heat and dryness flows to dryness? And claimed to be a "certified" energy consultant.

When you or your friend park their car outside at night, is it covered with moisture in the morning? Moisture in the Atmosphere.

bio_guy

Home inspections will never find all the problems all of the time. You just have to hope that they will find the serious and expensive ones. When they can't find a real problem, they nit pick to justify their presence.

For the OP, winter with sustained high indoor humidity in a heating environment is unusual in almost any situation. This makes it an emergency: "They are beginning to have mold problems". In the short term, get a dehumidifier or two before you have serious damage to the home. An even faster way to reduce the moisture is to ventilate as long as the absolute humidity is lower outdoors compared to indoors. Just open some windows. Identify the source of the problem before investing in an expensive remedy like a central dehumidifier.

For dehumidification and summer cooling, mini splits are certainly something to consider. I love all seven of mine and I ditched an existing duct system to get there. Efficient central dehumidifiers make less heat than common portables. Increased efficiency in moisture removal means less heat by nature. Efficient portables can be had from the same manufacturers as the central ones. The Energy Star web site rates them in liters/watt.

Coastal MA, been there and done that, but only in the Summer ca. Woods Hole. I am in South LA for several years now. I am not sure where is worse for humidity alone. For the combination heat and humidity, I do know. The coastal plain in the NE USA is very underrated as a noxious environment. After growing up in beautiful upstate NY (Nearer the North coast than the East coast), I was introduced to not only sustained higher humidity, but also poison ivy, ticks and chiggers on and near the East coast.

As another note, since living in South LA, I've come to appreciate that the air is much richer source of moisture than the ground, even when the latter is quite damp. With a cool structure and a high dew point and relatively fast moving air (relative to slow moving soil), you get fantastic moisture transfer rates. Old houses retrofitted with mechanical cooling and the requisite outdoor duct systems wreak condensation havoc. That is especially true because the ducts always leak and turn the duct systems into power vents drawing in moist, outdoor air in negative pressure areas.

icesailor

HRV's work the best. Or far better than opening a window in the cold winter. These will exhaust stale humid air and bring in fresh, dryer air. Heat flows to cold, dampness flows to dryness. Regardless of where you put the unit, the moist air will be absorbed by the dryer new air.

http://www.broan.com/products/product-line/balanced-ventilation-systems

barbarapratt

As a temporary fix, I bought them a dehumidifier for each level of the house and we will deal with the overall problem after the holidays. Thank you to each of you. Merry Christmas and Happy New Year.

bio_guy

HRVs and whole house dehumidifiers are great when you need them, but they are very expensive bandaids compared to a relatively cheap dehumidifier or two. The main thing to see here is that there is a problem with the house if it has excessive humidity in the high heating season At that latitude. A bandaid it what it needs right now, but it needs a real fix for the long term.

I obviously can't say for sure, but I doubt that the house is so tight that an HRV is needed. It is possible and a blower door test will reveal that. An inspection outfit with a certified energy rater/energy evaluator might be a good value for the OP.

What is really needed right now is knowledge. Is the home accumulating moisture because it is ultra tight? If not, where is the excessive moisture coming from? Now that I am considering all the angles, cracking open a window on the ground level, and another upstairs would be a really good experiment. If air infiltration is already normal to high, cracking a couple of windows won't change much. If the house is very tight, it will dry out. It is a pretty low cost test.

jumper

A lot of good ideas here but in the meantime I'd plug in a dehumidifier.

icesailor

Plugging in a dehumidifier in the winter heating season will lower your gas or oil bill. It will raise your electric bill.

Usually, if you have humidity issues in a home in the winter, they will be worse in the Summer. And running a dehumidifier in a home in the summer will definitely AC.

Discount what you want. If you have a home in the winter with high humidity, you have mold growing somewhere. Codes require many air changes per hour for health reasons. Some houses are so tight because of faulty codes, that they are really unhealthy to live in.