Too Much Humidity During Cold Spells

ced48

Well, I've got the house sealed up nice and tight, running warm, 120 degree water temperature in the baseboard, down from the old 170 degree standby, and now, lots of condensation on the the windows on cold mornings. Any suggestions?

Zman

What climate are you in?
I guess the hotter radiators did a better job of drying the air by the windows.
The route cause of your problem is likely the source of the moisture. I would look at crawl space floors with no vapor barriers or inadequately sealed concrete as likely sources.

dopey27177

If you seal the house to much you can't get rid of the humidity.

If you like a real tight house get a dehumidifier it will help keep you from growing mold in the house.

Jake

Jamie Hall

There is such a thing as too tight a house. The minimum air changes per hour should be 2 to 4 -- otherwise, as you are discovering, you indoor air quality can be really poor.

If your air changes are lower than that, you should consider a heat recovery ventilation system. This brings in outside air and exhausts building air, but allows the sensible heat to be recovered. Do NOT get latent heat recovery.

ced48

I'm in Rhode Island. Would a whole-house ventilation system make sense?

dopey27177

The recommendation by Jaime Hall is perfect if you can afford the cash.

If you have double hung windows you can open the top and bottom of one window in each room. About a 1/2" will do fine.

If you want to stay with a tight house gt a dehumidifier and install it in the largest room in the house.

Jake

ChicagoCooperator

Do you have thermopane glazing of some kind or storm windows? If you don't it's not surprising you have condensation. Are you running a humidifier, I don't think you mentioned that, but I assume you're not.

ced48

Yes, new Marvin widows-

pecmsg

Congrats you have a tight house but now you need mechanical ventilation.

HRV or ERV is needed.

JUGHNE

If the source of the humidity is from showering, cooking and you breathing you might get by with being sure you have adequate exhaust systems.
We have exhaust fans in every bath and the kitchen hood.
All have to be vented outside to daylight.
We have either motion sensors or 30 minute timers in the baths.
We have a 6" fresh air inlet in the basement.
This has taken care of most of our problems.

If you have taken all these steps then the HRV would be next, but IMO the exhaust system would come first.

Gordy

I think I’d see how a dehumidifier, and maybe running bath fans for extended periods helps before going all out on ducted Hrv.

Gotta a masonry fireplace? If so light that off the RH will drop in a hurry.

Big Ed_4

What percentage of humidity do you have to the outside temperature. ?

retiredguy

Houses that had a lot of infiltrated air were always dry inside and it did not depend upon the type of heat. Cold outside air when heated looses most of it's humidity when measured in percentage. A house too tight may use very little heat to maintain a given temperature, but the air quality suffers and can become dangerous for the occupants.

JUGHNE

Is your boiler vented up the conventional chimney?
The combustion air pulled into the basement usually dried things up.
But if it is running less, then fewer air exchanges on it's part.

Hap_Hazzard

Have you actually measured your indoor humidity? I struggle to keep mine above 45–50%. If it stays below 40% for any length of time, I get nosebleeds, and I still see condensation on some of my windows. When I see condensation on windows, I think bad windows, not too much humidity.

Your mileage may vary, of course, and my house is pretty far from being tight, but I wouldn't want to do anything to reduce indoor humidity during the typically dry winter months without measuring it first. Aside from causing health problems, too low humidity can damage acoustical musical instruments like guitars and pianos with wooden sounding boards. (I used to repair them.)

High humidity has downsides too, but you need to know what you're dealing with before you implement any remedies.

ced48

No, I don't have the actual humidity readings, going to check first of the week. Boiler is vented in a closed system, Lockinvar.

Big Ed_4

Yes lets see if there is problem. The problem starts when maintaining a comfortable level 45% as the outdoor temperature drops . You want to avoid condensation in the walls .

Solid_Fuel_Man

Condensating in the walls is from leakage, usually will be into the attic. If you have much leakage, you dont have high RH indoors. A properly build and insulated wall/ceiling (building envelope) doesnt allow warm humid air into the walls where it will condense and freeze.

ced48

Well, today outside temperature is 40 degrees, inside I have 49% RH. Guess I will have to wait for outside temperature to drop and see what I have-My guess is humidity is not going to be very high, and I do not have air leaks, just the opposite, so I am stumped-

RxRoy

What you describe sounds exactly like what I went through the first ten years in our new house. In the winter, the first thing we had to do every morning was mop the windows. Sometimes it would be so bad there would be lumps of ice at the bottoms of the windows.

I tried dehumidifiers in the worst rooms of the house. Made NO difference, except to run up the electric bill.

Finally, I installed a Fantech HRV. Within two days of running it, all the moisture problems were gone. Haven't mopped a window since, even at -10 outside. House feels much fresher as well.

I installed it myself. I had to drill two, six inch holes in my brick veneer to run the inlet and outlet ductwork. I tied the other two ports into the ductwork of the AC to distribute the fresh air through the house. You MUST use a manometer to set the flow rates, to avoid putting a vacuum or positive pressure on your house. You will need a drain or a condensate pump to drain the condensate.

Installing this was probably the most impactful improvement I've made to my house.

I attached a picture of the unit and the manual.

The bottom line was that my house was too tight, and it needed ventilation. Good luck!

Jamie Hall

Remember this: if you have significant air exchange (uncontrolled or controlled) from outside, the colder it gets outside, the lower the relative humidity in the house will be. If the house it tighter, it will have higher relative humidity. At some point in reducing infiltration, the humidity load from the occupants will increase the relative humidity enough that you will start to get condensation on cooler surfaces. No way around it -- except either dehumidification (which simply introduces a controlled cold surface somewhere) or increasing the air exchange with outside. You need to keep the dewpoint temperature (and hence, the RH) below the temperature of your colder surfaces.

ChrisJ

dopey27177 said:

The recommendation by Jaime Hall is perfect if you can afford the cash.

If you have double hung windows you can open the top and bottom of one window in each room. About a 1/2" will do fine.

If you want to stay with a tight house gt a dehumidifier and install it in the largest room in the house.

Jake

Is this a joke?

ChrisJ

ced48 said:

Well, today outside temperature is 40 degrees, inside I have 49% RH. Guess I will have to wait for outside temperature to drop and see what I have-My guess is humidity is not going to be very high, and I do not have air leaks, just the opposite, so I am stumped-

From what I can tell it's normal to get condensation on windows, even modern ones. There's only so much R value from the window and when it gets really cold out it's going to get some condensation on it. My parents have the same issue which is why my dad refuses to run a humidifier.

My RH in the winter often drops into the teens due to how drafty the house is. I'd love 30%, but it's not happening.

You probably have nothing to worry about. It's just the nature of the beast.

ethicalpaul

Hmm you have condensation on your windows Chris? I wouldn't expect that if you have a drafty house. I have a drafty small house (like I can hear it when the wind is blowing strongly), and I never have any condensation. I think I must have the equivalent of the 1/2" open window that Jake recommended.

My RH goes very low in the winter too. I keep sealing cracks when I find them and I am hoping for the day I see some condensation! Then I can stop sealing!!

ChrisJ

ethicalpaul said:

Hmm you have condensation on your windows Chris? I wouldn't expect that if you have a drafty house. I have a drafty small house (like I can hear it when the wind is blowing strongly), and I never have any condensation. I think I must have the equivalent of the 1/2" open window that Jake recommended.

My RH goes very low in the winter too. I keep sealing cracks when I find them and I am hoping for the day I see some condensation! Then I can stop sealing!!

Sometimes I do, yeah.
My cheap storm windows often get condensation on them.

Jamie Hall

I have some really expensive (high five into six figures) horror stories of what happens in historic structures when one pays more attention to relative humidity than one does to dewpoint...

Solid_Fuel_Man

Best for most structures to have a relatively low RH, but not so good for the occupants. I maintain 35% indoor through the winter. My windows will have the bottom 1/2"-1" of condensation when its below zero outside. Triple pane, but still the equivalent of an R4 at best.

This is why it is always best to have a slight vacuum on the interior of a building burning the heating months, this way, low humidity outdoor air is drawn in through cracks. If the building is a positive pressure the warm wetter air will be forced into the cavities and will condense somewhere which will be bad in many ways.

Leaky ceilings, from light boxes and those atrocious can lights, will tend to have warm air rise into the unconditioned space and leave behind the water along the way. This is again bad. This is also why attic ventilation is critical and not with a big fan creating a vacuum and no air inlets.

ced48

Dew point, rather than humidity, or both, got me confused. The house is tight, so tight, that when you close the front door, you have to give it a good push. Crack a window and it closes with ease. A small HRV system seems to be the answer.

pecmsg

That house requires a complete air change every 6 - 8 hours. This air change exhausts indoor pollutants and excessive CO and replaces them with fresh air. It also lowers the RH.

Gordy

Looking at your original post. In a nut shell the 170 awt to the baseboard was enough to increase the surface temperature of your windows. 50 degrees lower is huge. Couple that with sealing off infiltration.

It amazes me as we seek to tighten envelopes to the point of having to bring outside air in anyway. I know using an hrv/erv is controlled, and tempered, but so is natural infiltration.

Canucker

Natural filtration doesn't let me control when, where or how much infiltration though. I like the idea that I can design the opening for what I want that to be rather than just allowing it to enter wherever I missed sealing. I would think that would help the comfort levels, no?

Gordy

Oh I agree. It just seems counterintuitive is what I’m saying. I know you control how much, what the temperature, and humidity is the benefit.

Solid_Fuel_Man

It does seem like a fine edge on paper. In reality, the dramatically reduced fuel consumption more than pays off.

But yes, having to resort to added mechanical equipment to do something that was otherwise unnecessary seems counterintuitive. But with much smaller HVAC it more than works out.

That said..... my own home is near passivhaus insulated, but I passively ventilate with two critically placed vents. One on the first floor and one on the second. The intake is from a south facing covered porch which is generally 40 degrees above the OAT.

ChrisJ

Solid_Fuel_Man said:

It does seem like a fine edge on paper. In reality, the dramatically reduced fuel consumption more than pays off.



But yes, having to resort to added mechanical equipment to do something that was otherwise unnecessary seems counterintuitive. But with much smaller HVAC it more than works out.



That said..... my own home is near passivhaus insulated, but I passively ventilate with two critically placed vents. One on the first floor and one on the second. The intake is from a south facing covered porch which is generally 40 degrees above the OAT.

Is it really dramatically reduced fuel consumption?
It seems like something that would maybe pay for it self after a very very long time.


I'm talking a reasonably tight modern structure vs going too far. Not my drafty sieve.

Obviously increased comfort is another subject. Being able to bring fresh air in controlled, warm it or cool it and distribute it properly would have a fairly large effect.

I just don't see the cost savings.

Canucker

Definitely not a quick ROI on your investment if you're heating with gas. Where I am, the cost of it is pretty low. The comfort aspects are subjective. By that I mean that I probably value the increased comfort levels more than someone else might. It's what's driven the improvement around my house, more so than the payback

ced48

For me, I know an HRV system is not going to save me money, but cost me money to install and to operate. But having to dry your windows in the morning is a pain, and I know that moisture is not doing the house any good, or me, if mold is a by product of it. The house is kind of stuffy, and I think changing the air every 3 hours makes sense. I think this is what the future of new homes is heading for real quickly. In fact, I bet it becomes a code requirement before long.

Big Ed_4

I believe up in Canada it is code ..

Solid_Fuel_Man

> @ChrisJ said:
> (Quote)
> Is it really dramatically reduced fuel consumption?
> It seems like something that would maybe pay for it self after a very very long time.
>
>
> I'm talking a reasonably tight modern structure vs going too far. Not my drafty sieve.
>
> Obviously increased comfort is another subject. Being able to bring fresh air in controlled, warm it or cool it and distribute it properly would have a fairly large effect.
>
> I just don't see the cost savings.

I consume about half of the fuel a comparable home uses. The average home in my area burns 1,000 gallons of oil per winter. I burn 3 cord of wood, no other form of fuel or heat.

1000 gal of oil is 139,000,000 btu/year

3 cord of sugar maple is 72,000,000 btu/year

Assuming about equal efficiencies of oil and wood, which is possible with gasification.

Depending on your total cost of heat/year if you divide that in half the rest is money in your pocket. Cheap fuel makes that half not as big. But here in the expensive energy northeast, that 1,000 gallons is $2,500 this year.

Retrofitting may not yeald the same results. But in new construction, it pays to build well.

Jamie Hall

"it pays to build well". So true. In the northeast, in fact, an intelligently architected and sited house, built with attention to detail, can and arguably should be upwards of 70% semi-passive (that is using only a high volume low velocity blower to move warmth to shaded areas) solar heating. It's not hard to do (it is hard to get to 100%, but possible). Such a structure can look as much or as little like a traditional house as one likes, except more south glass (but not a solid glass wall!).

The problems come in retrofitting, as @Solid_Fuel_Man says. The obvious place to begin is better (or some!) insulation and improving (not necessarily replacing) windows and overall draught sealing -- paying at least some attention to providing adequate air exchange. Curiously, this is often actually harder to do in houses built in the last say 70 years or so than it is in earlier ones, particularly much earlier ones (18th and 19th century). Tearing out and replacing heating systems with something else is almost never cost effective, and rarely gives much efficiency gain, although replacing antiquated boilers and furnaces can produce significant efficiency gains, but is cost effective only when they require replacement due to failure. At least in my opinion...

Total

Big Ed_4 said:

I believe up in Canada it is code ..

Correct , it has been code for the last ten years .

Gordy

The United States missed out on making millions of homes the highest efficiency. Over the last 20 plus year building boom.