Insulation and window coverings... do they make a difference?

[masscom]

In your professional experience, how much does increasing attic insulation make a difference in the cooling of a home? How about window coverings?

These probably seem like "duh" questions, but I honestly don't know.

The insulation I have in my attic now is what the builder put in 30 years ago. According to my energy company audit, it's adequate; according to an a/c guy, it is not. I have floor-to-ceiling single-pane windows in the living room and kitchen with no window coverings.

If taking care of either of these would help lower the temperature in my home, I'd like to do so. On the other hand, I don't want to spend money on things that won't make a noticable difference when that money could be put toward a more efficient a/c unit.

Thanks for any input!

[REP]

Most people tell me my height is fine,but some have said I'm short.
What do you think??????

[Kevin O'Neill]

Window coverings definately help. So does insulation.

How much insulation do you have? What is the R-value?

How big are your windows. How many? Which way do they face?

I need numbers. Floor to ceiling is not a number. Give us inches wide by inches high.

[masscom]

I looked on the report from the energy company, and there is nothing written down about an R value. That's a good question. I know that one a/c person who looked in the attic said he could see spots where the insulation was so thin he could see the floor (ceiling?) beneath it.

In the living room, there is a bank of three windows facing west that's 76" tall by 135" wide. Each window iw 76" by 45". In the kitchen, facing north, there are two windows totalling 76" tall by 90" wide.

[skippedover]

Widows that face any direction but North should be covered to the extent you will allow. That is, shades andn/or reflective shades are ideal. They can greatly reduce the amount of sun load inside the rooms. Eliminating sun load reduces AC run times = money saved.

Attic insulation is also important with one caveat. Any holes or passages into the attic, under the existing insulation, should first be sealed. This is helping to 'seal the living space envelope' and stop the exfiltration of air. It's more beneficial in winter heating rather than summer cooling but exfiltration is an expensive heat robber in winter. Once the envelope is sealed, then insulate the daylights out of the attic. The more, the better.

[masscom]

Thank you so much! That's just what I needed to know. I'll get right on that insulation! I assume if there were any cracks, I could see them in my ceiling below, and I don't. Great advice.

Do you have an opinion about double-pane windows as compared to window coverings as far as keeping out heat?

[classical]

Thank you so much! That's just what I needed to know. I'll get right on that insulation! I assume if there were any cracks, I could see them in my ceiling below, and I don't. Great advice.

Do you have an opinion about double-pane windows as compared to window coverings as far as keeping out heat?

Any unsealed penetration into the attic needs sealing not just cracks you can see light through.

Every plumbing or electrical penetration the top of any wall needs to be sealed. Search BPI.org for a better understanding.

[energy_rater_La]

Do you have an opinion about double-pane windows as compared to window coverings as far as keeping out heat?


that is pretty general..as is asking for an opinion here!
What type of windows do you currently have?
single pane?
what type of window frames?
what is your location?
what are the recommended R-values for insulation in your climate?

it will always be better for old windows to keep the heat from entering the window.
once the heat enters the window and the space to be conditioned it is harder to condition the living space.

there can be up to a 20% savings just by plantings that shade windows in the
summer. for instance I have bananna trees that get high enough by mid July to
shade the front windows and front door.. in the winter I have a windbreak of
evergreen trees. the former has more impact than the latter..because of the length
of the cooling season in my location. I consulted a solar plantings guide for some of the
plantings, others were just luck!

single wood windows get a bad rap all the time. but they can be weatherstripped
caulked and sealed pretty well. once this is done window tints can be installed
to reflect heat out..my climate or into the house..for cold climates. these tints
have improved a lot in the past few years.

single metal windows may be newer, and have a tighter fit as far as air leakage but the metal frame conducts heat/cold which makes these windows a real hot/cold spot.

single windows always condensate and in extreme cases can rot out window sills &
cripples under windows.
in the summer the glass condensate to exterior..in winter to the interior. simple thermodynamics.
it is when you step upto a double paned window that the condensation
is stopped..in most cases..by the insulating air space between window panes.
adding low e and argon gas improves the thermal efficiency of the glass..
selecting the proper frame is also important.
wood frames & vinly being poor conductors of hot/cold is a better choice than metal
frames which is an excellent conductor of hot/cold.

best of luck.

[masscom]

I have single-pane windows (as I described in an earlier post) that are 76" X 45 inches each -- three along my living room and two in the kitchen. The frames are aluminum. My house was built in 1984, and I'm sure the windows are original. There is some kind of film on them, but I don't know if it's to keep out the sun or for security. I live in Florida.

The sun pours in the living room windows in the afternoon. I was going to look into double-pane windows which one hvac guy told me would keep out as much heat as a wall. Then the energy company person came out to do an audit and told me that double-pane windows wouldn't keep out any heat, and I should get window coverings. Hence my question.

I can see there are differing opinions. I appreciate everyone's input.

[classical]

I have single-pane windows (as I described in an earlier post) that are 76" X 45 inches each -- three along my living room and two in the kitchen. The frames are aluminum. My house was built in 1984, and I'm sure the windows are original. There is some kind of film on them, but I don't know if it's to keep out the sun or for security. I live in Florida.

The sun pours in the living room windows in the afternoon. I was going to look into double-pane windows which one hvac guy told me would keep out as much heat as a wall. Then the energy company person came out to do an audit and told me that double-pane windows wouldn't keep out any heat, and I should get window coverings. Hence my question.

I can see there are differing opinions. I appreciate everyone's input.

Double pane windows do keep out heat how much depends on many factors all windows are not created equal. Windows are however a very poor investment purely from an energy savings point but have other redeemimng values.

For you the best bang for the buck would be solar screen which are much more effective than solar film. Another benefit is the screens came be removed during the cooler months to increase light and to take advantage of solar gain. You should check with your HOA if you have one to see if they have restrictions.

If your energy auditor was any good they should have pointed out areas of the home that need sealing to prevent uncontrolled air and moisture infiltration.

[belliott]

Insulation is your friend, most homes do not have enough in the attic. If you have an older home you may even check the condition of your exterior wall insulation. It can sag and break down over time.

Poor windows with no coverings can have a huge impact on your utilitie bills.

[masscom]

Good information, guys. Thanks!

Yeah, I expected the energy auditor to point out places that needed sealing, but that didn't happen.

I'm getting right on that attic insulation! I'm not even sure there is insulation between my walls. (What I don't know about houses could fill a book.) But I'm sure the insulation company could look at that.

Looks like some kind of window coverings are in order too.

This is my first house. I wonder if it ever gets to the point where there aren't a bunch of major things you have to do, house-wise.

Again, thanks.

[belliott]

This is my first house. I wonder if it ever gets to the point where there aren't a bunch of major things you have to do, house-wise.

The joys of home ownership can be costly. Get it the way you want it. After that maintain it.

[02powerstroke]

biggest loads of a building are windows typically, unless you are designing for a kitchen etc... Windows in a home will make a large difference on your load

[masscom]

Great info! I'll look into window coverings too. Thanks for taking the time to reply!

[Kevin O'Neill]

Single pane wood windows with good quality storm windows often have lower cooling loads than double pane wood windows. At least that is what Manual J says.

[Shophound]

Strictly from a return on investment (ROI) basis, replacing poor window assemblies with great ones have a long payback period. However, the comfort gains are tremendous, especially during cold weather. In hot weather, new assemblies will reduce cooling demand and again, return comfort dividends beyond the ability to be measured by utility bill savings.

That said, if attic insulation is marginal to poor, I would start there first. Being that Florida is primarily a cooling season state, and has perhaps the southernmost latitudes in the US, where sun angle is very high in summer, reducing heat transfer into the house from the attic is a great place to start.

[02powerstroke]

Single pane wood windows with good quality storm windows often have lower cooling loads than double pane wood windows. At least that is what Manual J says.

yeah, Have to look at the R values and solar load that each window takes... Single pain windows are very inefficient

Maybe Manual J is considering the air gap between the two windows to be greater than that of a 2-pane window?... not sure why it would model it that way... the R value will be what govern's the energy transmitted through the window...

[Kevin O'Neill]

yeah, Have to look at the R values and solar load that each window takes... Single pain windows are very inefficient

Maybe Manual J is considering the air gap between the two windows to be greater than that of a 2-pane window?... not sure why it would model it that way... the R value will be what govern's the energy transmitted through the window...

Yes, storm windows give you a big air gap. They must be properly installed and sealed, though.

[Kevin O'Neill]

Strictly from a return on investment (ROI) basis, replacing poor window assemblies with great ones have a long payback period. However, the comfort gains are tremendous, especially during cold weather. In hot weather, new assemblies will reduce cooling demand and again, return comfort dividends beyond the ability to be measured by utility bill savings.

That said, if attic insulation is marginal to poor, I would start there first. Being that Florida is primarily a cooling season state, and has perhaps the southernmost latitudes in the US, where sun angle is very high in summer, reducing heat transfer into the house from the attic is a great place to start.

It depends on the cost for replacement windows. Around here I have seen costs of 189.00 to over $1,000.00 for vinyl replacement windows. I paid less than $300.00 each installed and am very pleased with the improved comfort. I went from single pane wood windows with cheap metal storm windows to double pane vinyl, low-e, argon filled with a 1/2" gap and a U-Factor of 0.30. Plus the drafts are gone and outside noise is almost gone! I love it!!

[02powerstroke]

I plan on replacing my old double pane wood windows with a double pane low e window very soon... I have a couple southwest facing windows.. so it will make a large difference

[classical]

First off windows do not have an R-value they have a U-factor there is a difference. Storm windows only increase the u-factor .5 % over standard single pane windows. An air gap does not reduce heat transfer noble gases (Argon Krypton) do because they are heavier. When cheap double pane windows lose their seal and the noble gas escapes and are replaced with normal atmospheric air they lose a considerable percentage of their U-value.

Insulation installed misaligned or with other means of air infiltration loses 70% to 80% of its rated R-value; the same is true of windows that are not properly sealed.

[02powerstroke]

First off windows do not have an R-value they have a U-factor there is a difference. Storm windows only increase the u-factor .5 % over standard single pane windows. An air gap does not reduce heat transfer noble gases (Argon Krypton) do because they are heavier. When cheap double pane windows lose their seal and the noble gas escapes and are replaced with normal atmospheric air they lose a considerable percentage of their U-value.

Insulation installed misaligned or with other means of air infiltration loses 70% to 80% of its rated R-value; the same is true of windows that are not properly sealed.

The R value is just the inverse of the U value so whats the difference?

Having an air gap is better than no air gap at all... Yes there is a difference between air and a more dense gas but having an air gap will reduce the heat transfer through the window when compared to a window with no air gap

[classical]

The difference is R-value is resistance to heat and U-factor is transference of heat.
A storm window over a single pane window will increase the U-factor by .5 or from .5 to 1.0 which in terms of stopping radiant heat is virtually nil. When a cheap double pane window loses its noble gas the window than becomes nothing more than a single pane window with a storm window and the only benefit it has will be derived from the E-coating if it has one. If the window is not properly sealed and insulated around the frame and casement the window is basically ineffective. Contrary to what many think stuffing insulation around the frame does not mean the unit is sealed or insulated.

[02powerstroke]

All im saying is that the R value is the oppsite side of the coin from the U value... Either gives a specification on what the window is capable of

[Mr Bill]

I think the best way to insulate, is just build your home with double concrete walls no winders at all, and stuff down in between the walls, silica and carbon aerogel and pack your attic with the same, then you should be able to cool and heat a 4000 sq. ft. home with a 1.5 ton system. :D

[masscom]

If I'm understanding, sounds like:

1) I need to get more insulation in my attic.

2) I need to get some kind of window coverings.

3) Double-paned windows, with argon and E-coating, may or may not make a big difference in keeping a house cooler. That is getting into the area of opinion.

Thanks for all the input!

[02powerstroke]

depending on windows are installed right now, the windows could make a huge difference

[commerce48]

Single pane wood windows with good quality storm windows often have lower cooling loads than double pane wood windows. At least that is what Manual J says.

Yes, storm windows give you a big air gap. They must be properly installed and sealed, though.

I went from single pane wood windows with cheap metal storm windows to double pane vinyl, low-e, argon filled with a 1/2" gap and a U-Factor of 0.30. Plus the drafts are gone and outside noise is almost gone! I love it!!

I would suspect that Manual J is overestimating the effects of available storm windows. They are very poorly constructed and it is common to see daylight in the seams. They deliberately place weep holes, and I have seen other deliberate hole punches by the manufacturers - whose purpose is obscure to me, perhaps an attempt to balance pressures or maybe the dew point?

Necessarily, the window panels fit relatively loosely to be able to raise and lower the storms. It is easy to duplicate a wind gust by pushing on the outside of a storm window and see that the window moves away from the pile weatherstripping. Which means at the time you need it the most, wind is penetrating past the storm.

Which is why you and everyone else notices a comfort improvement in the house when upgrading windows.

I'm going a different route and replacing my existing aluminum storms. Building wood storms that will be fixed into place permanently and sealed. One panel will be removable from the inside so that I can place screens seasonally. This panel will have silicone seals and be fixed into place tightly (no movement with wind).

That solution should prove just as comfortable in the short term as new double hung windows, and may actually have a higher U value. The cost is about a fifth of what wood double hungs would have cost. Infiltration rates should also be equivalent, and stay lower going forward than new windows would.

[Kevin O'Neill]

The difference is R-value is resistance to heat and U-factor is transference of heat.
A storm window over a single pane window will increase the U-factor by .5 or from .5 to 1.0 which in terms of stopping radiant heat is virtually nil. When a cheap double pane window loses its noble gas the window than becomes nothing more than a single pane window with a storm window and the only benefit it has will be derived from the E-coating if it has one. If the window is not properly sealed and insulated around the frame and casement the window is basically ineffective. Contrary to what many think stuffing insulation around the frame does not mean the unit is sealed or insulated.

Actually storm windows will DECREASE U-Value. Note: 1/U=R. A decrease in U factor will Increase R-Factor.

My windows have a U-Factor of 0.3.

That is equal to an R-Factor of 3.33...

[energy_rater_La]

A storm window over a single pane window will increase the U-factor by .5 or from .5 to 1.0 which in terms of stopping radiant heat is virtually nil.

the reason a double paned window performs better than a storm over a single pane
is that the two panes are close together. lowe and argon help to keep air at rest
and glass unit is sealed.
the larger the gap between two window panes such as storm over single pane window
the more convenctive current between the two glass surfaces.
these windows perform no were near the same as an insulated glass unit.
as stated lowe argon windows have ufactors and solar heat gain coefficinets of
.30 and less..a single glass window with a storm will be at least .50 and higher
depending on if the window frame is wood or metal. metal conducts wood doesn't.

powerstroke you should take a look at the thread I started on a home that just
changed windows and the actual savings..not huge..something like 14.8%
energy savings..not the best investment nor bang for the buck.

[Kevin O'Neill]

Are you saying adding a storm window to a single pane wood window will increase U Factor and heat transfer?!!!

[commerce48]

A storm window over a single pane window will increase the U-factor by .5 or from .5 to 1.0 which in terms of stopping radiant heat is virtually nil.

the reason a double paned window performs better than a storm over a single pane is that the two panes are close together. lowe and argon help to keep air at rest and glass unit is sealed. the larger the gap between two window panes such as storm over single pane window the more convenctive current between the two glass surfaces. these windows perform no were near the same as an insulated glass unit.


My primary goal is to stop infiltration. But a dead air space can only help insulate my house. My current single pane wood windows are already surprisingly tight. I will do a followup blower door to measure any improvement.

In addition, my wood framed storms will have lower transmission losses than the aluminum storms could dream of.

The literature I've seen on new windows show increases in infiltration rates over the years. That cannot be the case with my design. So I'm expecting that over decades, my energy costs will add up. Plus I'm spending much less up front - not that I'm going for ROI. Personal comfort, and reduced drag on society.

[commerce48]

Are you saying adding a storm window to a single pane wood window will increase U Factor and heat transfer?!!!

Rather obviously, I stated that incorrectly.

[Kevin O'Neill]

It wouldn't be the first time something obvious turned out to be wrong. I just wanted proof. But Energy rater la said the same thing , I think.

[shwung79]

Cant hurt.

[belliott]

I'll give you an idea of savings.

I had to do some work on a customers plumbing system today. I've done lots of work for this guy in the past. During the spring he had all his windows replaced and had insulation added to the attic. One of the bedrooms in the home had no insulation in the attic. NO changes have been made to the HVAC system. I asked him if he had noticed a diffrence in his utility bills.

We have had record breaking heat this year and the summer was fairly mild last year, yet his electric bill was 26 dollars less for July 2010 than July 2009.

In the past he has set his thermostat at 68 to keep the home comfortable,it is now set at 74.

He also replaced all of the exterior doors on the home. I don't know the exact numbers but it seems like he replaced 35 windows and 4 doors.

[shwung79]

That is impressive. I wonder what the investment was on 35 windows though?

[masscom]

That's really helpful to know! Since my focus is on getting it cooler in here and not lowering my electric bill enough to get a return on investment, it's good to know that new windows make such a difference. I think I'll look into those as well. No point in spending money on window coverings that could go toward windows, and I might just need the big ones replaced. Great information.

[dan sw fl]

Most people tell me my height is fine,but some have said I'm short.
What do you think?????? Were they referring to your height or SIGHT when they called short

[dan sw fl]

I have single-pane windows (as I described in an earlier post) that are 76" X 45 inches each -- three along my living room and two in the kitchen. The frames are aluminum. My house was built in 1984, and I'm sure the windows are original. There is some kind of film on them, but I don't know if it's to keep out the sun or for security. I live in Florida.

The sun pours in the living room windows in the afternoon. I was going to look into double-pane windows which one hvac guy told me would keep out as much heat as a wall. Then the energy company person came out to do an audit and told me that double-pane windows wouldn't keep out any heat, and I should get window coverings. Hence my question.

I can see there are differing opinions. I appreciate everyone's input.

Shading and tinting windows is MUCH more significant in decreasing heat gain.

Double pane windows is useful in Northern climates where the temperature difference is 60 to 100'F.

FL temperature difference can be Negative or close to zero during late evening / night in the Summer ( 76'F inside, 70'F - 75'F outside). Day time difference is probably in the range of 10' to 15'F.

Double-pane will prevent "window sweating" if you are keeping the inside temperature < 73'F, like in a meat locker or in many cases, restaurants.

[masscom]

I couldn't figure out the height analogy.

[masscom]

An expert from Florida!

My main problem is in the afternoon and evening when it's in the 90s outside and I want it to be 70 inside. Yes, like in a restaurant or bank! I've always wondered how they can get it so nice and cold in those places. I'm trying to do what I can to lower the inside temperature before I decide on the major expense of a bigger a/c unit which will probably require bigger ductwork as well.

I have some kind of film on my windows that came with the house. I guess I could have someone come out and tell me if what I have is the best I can do.

[Shophound]

Build a trellis over the exterior of the windows that get the most sun and let a climbing vine grow on it, like trumpet vine or bougenvilla or wisteria.

If you keep the sun out to begin with, you won't need to fight trying to block it out from the inside, or with tints.

[masscom]

Sounds like a great idea and also pretty, but the big windows actually go out to a 23' X 22' screened-in patio.

[mattcage]

I have replaced most of my windows with vinyl (3 doors (wood to metal) and nice storm doors also) and tinted them. I have a 80" x 110" patio door (south facing) that I cannot afford to replace and tinted that also.

I turned off my air conditioner and dehumidifier while the guys where doing the work and expected to come home to a hot house after work. With no ac and no dehumidifier for the day, the house was very pleasant when I walked in. I didn't turn the ac when I got in and just lounged around enjoying things. I finally turned on the the ac and dehumidifier to dehumidify the house and it was quite chilly at 78 on the thermostat. It was flat out brutal during the days the work was being done.

Tint salesman really pushed the ceramic tint, but I went with old traditional metallic film as it had better heat rejection specs than the solar. I wished I had done this 5 years ago.

[masscom]

Thanks, Mattcage. Interesting. I might do some research on window films today, including the kind you suggest. I'll also have to see if it can be applied over whatever film is on there now.

[Mr Bill]

Build a trellis over the exterior of the windows that get the most sun and let a climbing vine grow on it, like trumpet vine or bougenvilla or wisteria. If you keep the sun out to begin with, you won't need to fight trying to block it out from the inside, or with tints.

O heck, that's to easy, keep that easy stuff out of here, we will loose all our scientists here, they will get bored and go home. :D :D :D

[mattcage]

Thanks, Mattcage. Interesting. I might do some research on window films today, including the kind you suggest. I'll also have to see if it can be applied over whatever film is on there now.

The same film that I used,Madico SRS220, also comes in a external version.

I am very happy with this film and highly recommend it. My guy was really pushing the ceramics as they are not much darker than saran wrap it seems, but they don't have the best performance as compared to the metallic film. 60% as opposed to 80% total solar heat rejection. The metallic can be off puting to some people or if you live in a swanky neighborhood it might not fly with the HOA or the Exchequer. I wanted the best bang for the buck and that was metallic. I live in a crappy area, the less I see of my neighbors the better.

Matt

[energy_rater_La]

numbers from Remrate the software Resnet mandates
for raters:
single wood uvalue .90 shgc .65

single wood with storm uvalue .80 shgc .50



single metal uvalue 1.30 shgc .80

single metal with storm uvalue 1.09 shgc .72
(differece in uvalue is conductivity of metal frame)



double lowe vinyl frame uvalue .36 shgc .35

double low e argon gas vinyl frame uvalue .30 shgc .30

I'm no expert, but I do know that the distance between the glass
panes is directly linked to performance.
in an Insulated Glass Unit (double paned or triple pane) the air space
has a minimum and maximum distance. Too close and there is an issue..
too far and convective currents set up between the panes. this lowers
performance.
IGU's and single windows with storm windows are different dynamics.

now a good investment in my climate is a solar screen...next to plantings
awnings & exterior shading the solar screens beat the heat before it enters
the building envelope (where it costs to condition this gain)
heres arnother example (again from remrate library)

single metal with solar screen uvalue 1.09 shgc .50
solar screen lowers shgc by .30 as compared to single metal window.

these numbers are the ones we use for existing homes deciding
between changing windows as opposed to solar screens or tints.
it all depends on homeowner's intent and condition of existing windows.

new window info can be modified within remrate based only on NFRC (national fenestration rating council..pardon mispelling) info.
even with uvalues and shgc info on NFRC sticker, we still test air tightness
and verify numbers.

(shgc solar heat gain coefficient)

[Shophound]

Sounds like a great idea and also pretty, but the big windows actually go out to a 23' X 22' screened-in patio.

May I assume this screened in patio is covered? If so, and the windows in question face west, can I also assume you don't get sunlight through these windows until late in the afternoon?

AND...if that happens, build the trellis along the western face of your screened in porch. When the plants mature it will keep the hot western sun from reaching deep into your porch and thus the windows.

I built a simple trellis on my deck, which is on the west side of my house. Two posts with a cross tie on each, with clothesline strung between each cross tie. The wisteria nearby is already sending feelers out onto the lines for an eventual takeover. :)

[masscom]

Huh. I never thought of that. That's not a bad idea at all!

I'm learning so much from this site. The idea of keeping the sun out from the outside had never occurred to me.

Thanks so much!

[hearthman]

You can also plant deciduous trees on the south face, esp. in front of large windows. Passive solar.... When the leaves drop off in the Fall, it lets in solar heat when you want it most.
Blinds do help also.
Light colored roofing helps in hot climates/ dark roofing for heat gain in northern climes.
Vines do work but boy they can take over the world. If you need it in a hurry, just get some kudzu from the South. I assure you any Southerner would be glad to give you all they have. :LOL:

hth,

[dan sw fl]

O heck, that's to easy, keep that easy stuff out of here, we will loose all our scientists here, they will get bored and go home. :D :D :D

Mr. Deep Pockets,

The only MANLY solution is a small Chiller for Anyone who
thinks < 73'F is CooL.

Your expression of appreciation for such a Great Idea
is gladly accepted in advance.