Condensation on skylights
 

Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

"Mike Hartigan" wrote in message

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

Any way you can insulate or make a barrier with plastic sheeting? Since you
can't change the laws of physics, the only thing you can do is add a thermal
barrier. If it is the glass causing the condensation, double pane would
help. If it is the frame, you have to make a barrier of sorts.

Mike Hartigan wrote:
Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

You are on the right track. I would start by seeing if there is any way
to insulate the skylights themselves. Adding thermo glass and replacing
thing like aluminum frames with a less conductive material like plastic.
would be a good start.

Adding an additional window below that one and allowing some air past
the existing window should also help. The temp difference will be less for
the new window and the air in-between will be less cold that outside and
dryer than inside. Note: cold air hold less moisture than warm. Even if it
is snowing outside with 90% humidity, if you bring that air inside it
becomes very dry as it warms up. The condensation is coming from that 40%
humidity 70º comes in contact with the 10º glass and frame and it cools to
10º and it can no longer hold the same total amount of moisture as it is now
over 100º humidity.

Your idea of fans (including the ceiling fan) warms the window a little
and that is why you have less condensation. If you can warm the Frame and
glass enough it would work. Also heat lamps or any heat source would help.

However the real answer are modern skylights designed to handle your
conditions without condensation.


--
Joseph Meehan

26 + 6 = 1 It's Irish Math

'I also have a central humidifier which does a superb job (Craftsman
3000, 14 years old, foam wheel type).'

Being in the Trade, i can tell you that this type of humidifer is the
worst one. WHenever the humidifer wheel is not turning, you have
standing water which is a breeding ground for bacteria , algae, and mold
to form. Then it gets delivered thru your duct system by the furnace
blower to all areas of your house. Just thought id give you a headsup
so you dont get an airborne disease(s). Aprilaire Brand is the best to
have to prevent this entirely.

Mike Hartigan wrote:

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other... Is this a common problem with a
common solution that maybe I'm just not aware of?

You might try an anti-static spray on the rug, eg salt water.

Nick

"Mike Hartigan" wrote in message
Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

It would be interesting to know if your skylights are plastic/acrylic or
glass. Going out on a limb here, I would venture to guess your lights are
of the acrylic/plastic dome stile.

Pella, Andersen and Velux which are glass, manufacture their skylights with
a small tray at the bottom of the light. This tray collects condensation to
help prevent those drips, the condensation evaporates out of the tray. I've
seen the trays overflow when there is too much humidity in the home.

In twelve years since you've gotten yours, there has been major improvements
to thermal breaks, R factors and general overall insulating factors in
skylights with glass. If the problem you have can't be tolerated, I would
look at the better skylights. In my book Velux is the best.

In article ,
says...
'I also have a central humidifier which does a superb job (Craftsman
3000, 14 years old, foam wheel type).'

Being in the Trade, i can tell you that this type of humidifer is the
worst one. WHenever the humidifer wheel is not turning, you have
standing water which is a breeding ground for bacteria , algae, and mold
to form. Then it gets delivered thru your duct system by the furnace
blower to all areas of your house. Just thought id give you a headsup
so you dont get an airborne disease(s). Aprilaire Brand is the best to
have to prevent this entirely.


Thank you for your concern, but I'm aware of these problems and I
tend to be aggressive with regard to minimizing them. I clean and
disinfect the reservoir monthly, more often during less-used periods.
Aprilaire does, indeed, eliminate this problem and when this unit
finally dies, I'll probably go that route.

--
-Mike

In article ,
says...

"Mike Hartigan" wrote in message

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

Any way you can insulate or make a barrier with plastic sheeting? Since you
can't change the laws of physics, the only thing you can do is add a thermal
barrier. If it is the glass causing the condensation, double pane would
help. If it is the frame, you have to make a barrier of sorts.

These are fairly recent technology with respect to construction and
materials (about 12 years old). Veluxe (I don't recall the model#)
double pane, aluminum/wood construction. Although perhaps a
plexiglass indoor 'storm window' type solution might help - along the
lines of your plastic sheeting suggestion. That would keep some of
the warm air away from the glass.

Thanks

--
-Mike

In article ,
says...
Mike Hartigan wrote:
Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

You are on the right track. I would start by seeing if there is any way
to insulate the skylights themselves. Adding thermo glass and replacing
thing like aluminum frames with a less conductive material like plastic.
would be a good start.

As I said in a response to another post, it's a double pane,
aluminum/wood construction. Technology-wise, it's already designed
to minimize such problems but, physics being what it is, it doesn't
eliminate the problem.

Adding an additional window below that one and allowing some air past
the existing window should also help. The temp difference will be less for
the new window and the air in-between will be less cold that outside and
dryer than inside. Note: cold air hold less moisture than warm. Even if it
is snowing outside with 90% humidity, if you bring that air inside it
becomes very dry as it warms up. The condensation is coming from that 40%
humidity 70º comes in contact with the 10º glass and frame and it cools to
10º and it can no longer hold the same total amount of moisture as it is now
over 100º humidity.

I understand the physice behind the problem (somehow, it sounds so
much more complicated when you try and explain it ;)

Your idea of fans (including the ceiling fan) warms the window a little
and that is why you have less condensation. If you can warm the Frame and
glass enough it would work. Also heat lamps or any heat source would help.

The ceiling fan works fairly well and I've also closed the register
vents in this room, which will reduce the temperature by, maybe 2-3
degrees. More significantly, however, there will be less humidified
air directed into this room. We'll see what happens.

However the real answer are modern skylights designed to handle your
conditions without condensation.

Again, these are 'modern' skylights.

--
-Mike

In article ,
says...

"Mike Hartigan" wrote in message
Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

It would be interesting to know if your skylights are plastic/acrylic or
glass. Going out on a limb here, I would venture to guess your lights are
of the acrylic/plastic dome stile.

Pella, Andersen and Velux which are glass, manufacture their skylights with
a small tray at the bottom of the light. This tray collects condensation to
help prevent those drips, the condensation evaporates out of the tray. I've
seen the trays overflow when there is too much humidity in the home.

In twelve years since you've gotten yours, there has been major improvements
to thermal breaks, R factors and general overall insulating factors in
skylights with glass. If the problem you have can't be tolerated, I would
look at the better skylights. In my book Velux is the best.

These are Velux double pane glass, aluminum/wood construction. No
drip trays, though.

--
-Mike

From: Mike Hartigan


In article ,
says...

"Mike Hartigan" wrote in message
Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

It would be interesting to know if your skylights are plastic/acrylic or
glass. Going out on a limb here, I would venture to guess your lights are
of the acrylic/plastic dome stile.

Pella, Andersen and Velux which are glass, manufacture their skylights
with
a small tray at the bottom of the light. This tray collects condensation
to
help prevent those drips, the condensation evaporates out of the tray.
I've
seen the trays overflow when there is too much humidity in the home.

In twelve years since you've gotten yours, there has been major
improvements
to thermal breaks, R factors and general overall insulating factors in
skylights with glass. If the problem you have can't be tolerated, I would
look at the better skylights. In my book Velux is the best.

These are Velux double pane glass, aluminum/wood construction. No
drip trays, though.

--
-Mike

Are these skylights at the top of a sheetrock "tunnel" from a normal flat
ceiling to the roofline?

If so, I'd access the attic space surrounding these tunnels and insulate them.

In article ,
unkbloc says...
From: Mike Hartigan


In article ,
says...

"Mike Hartigan" wrote in message
Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

It would be interesting to know if your skylights are plastic/acrylic or
glass. Going out on a limb here, I would venture to guess your lights are
of the acrylic/plastic dome stile.

Pella, Andersen and Velux which are glass, manufacture their skylights
with
a small tray at the bottom of the light. This tray collects condensation
to
help prevent those drips, the condensation evaporates out of the tray.
I've
seen the trays overflow when there is too much humidity in the home.

In twelve years since you've gotten yours, there has been major
improvements
to thermal breaks, R factors and general overall insulating factors in
skylights with glass. If the problem you have can't be tolerated, I would
look at the better skylights. In my book Velux is the best.

These are Velux double pane glass, aluminum/wood construction. No
drip trays, though.

--
-Mike

Are these skylights at the top of a sheetrock "tunnel" from a normal flat
ceiling to the roofline?

If so, I'd access the attic space surrounding these tunnels and insulate them.

The ceiling is sloped parallel to the roofline, about 25 degrees.
The space between the joists is insulated with 11.5" fiberglass with
a suitable vapor barrier. There's really no room for improvement
here. I suspect that insulation is not the problem problem, since
the condensation is occurring only on the glass.





--
-Mike

I think you actually had the best answer in one of your own posts, namely
that the temperature will need to be a bit lower in that particular room.
That's about the only way to drop the dew point near the skylight without
decreasing
the humidity housewide. Any air mixing you can get from ceiling fans or
more focused
air drivers will help as well. By the way, in winter, you would fans moving
air upward to
displace the moist strata at the ceiling.

Bill


"Mike Hartigan" wrote in message
ews.com...
Well, here we are in the midst of another winter of sub-zero
temperatures and I'm having the same problem I have every year at
this time. It didn't go away by itself again this year, so I thought
I'd ask for suggestions.

I built an office addition on my house about 12 years ago. There are
two skylights in this room (the preferred lighting alternative to
windows overlooking the side of the neighbor's house). I also have a
central humidifier which does a superb job (Craftsman 3000, 14 years
old, foam wheel type). As the outside temperature goes down, so goes
the humidistat (that's normal). This seems to keep the condensation
on the skylights to a minimum. Indeed, I use the condensation on the
skylights as a guide to setting the humidistat (simple, yet
effective). In case you haven't already guessed, these skylights are
the most condensation-prone sites in the house.

When the temperature gets into the single-digits or below, I have the
conflicting problems of dripping skylights and static discharges
whenever the kids touch other (which seems to happen a lot more often
under these conditions, but I digress). I dont want to reduce the
humidity further, since the static discharges suggest that it's
already too low. I don't want to increase it, since the condensation
suggests that it's already too high.

I have a ceiling fan in that room, and that seems to reduce the
problem somewhat (it doesn't eliminate it), but I'd like a 'better'
solution. Perhaps something to apply heat to those skylights, or
maybe small fans directed at them? Is this a common problem with a
common solution that maybe I'm just not aware of? I've searched and
can't really find anything that addresses this.

Thanks
-Mike

bill a wrote:

I think you actually had the best answer in one of your own posts, namely
that the temperature will need to be a bit lower in that particular room.

Perhaps you mean "higher."

That's about the only way to drop the dew point near the skylight...

Why would that change the dew point?

Nick

Any way you can insulate or make a barrier with plastic sheeting? Since you
can't change the laws of physics, the only thing you can do is add a thermal
barrier. If it is the glass causing the condensation, double pane would
help. If it is the frame, you have to make a barrier of sorts.

You don't need a thermal barrier, you need a VAPOR barrier.
Make a wood frame that will fit over, or inside, the
window well, and cover it with plastic. Make
a small cloth bag, or stuffed toy or something, and
fill it with rice, or dessicant. Toss that on top
of the plastic, fit the panel in place, and caulk with
that nifty removable caulk. The plastic keeps
household air from circulating against the window,
but lets enough heat through so that you don't get
condensation on the plastic. The bag of dessicant
eats whatever moisture does make it into the (now closed)
space. Don't let the bag rest against the edge,
it shouldn't touch anything but plastic.

--Goeedjn

warmer air holds more moisture, greater temperature differential at the
glazing


bill


wrote in message
...
bill a wrote:

I think you actually had the best answer in one of your own posts, namely
that the temperature will need to be a bit lower in that particular room.

Perhaps you mean "higher."

That's about the only way to drop the dew point near the skylight...

Why would that change the dew point?

Nick

bill a wrote:

warmer air holds more moisture, greater temperature differential at the
glazing

Warmer is better because that raises the glass temp, but that won't change
the dew point temperature of the air, ie the temp when dew forms, which
only depends on the actual moisture content, vs how much the air can hold.

bill a wrote:

I think you actually had the best answer in one of your own posts, namely
that the temperature will need to be a bit lower in that particular room.

Perhaps you mean "higher."

That's about the only way to drop the dew point near the skylight...

Why would that change the dew point?

Nick

whatever you want to believe is OK with me :)

Bill


wrote in message
...
bill a wrote:

warmer air holds more moisture, greater temperature differential at the
glazing

Warmer is better because that raises the glass temp, but that won't change
the dew point temperature of the air, ie the temp when dew forms, which
only depends on the actual moisture content, vs how much the air can hold.

bill a wrote:

I think you actually had the best answer in one of your own posts,
namely
that the temperature will need to be a bit lower in that particular
room.

Perhaps you mean "higher."

That's about the only way to drop the dew point near the skylight...

Why would that change the dew point?

Nick