The class was excellent.*  Really excellent.  Not only was an enormous amount of knowledge expressed - and mostly absorbed! -  over the course of 6 days, but the clarity of thought you need to accurately apply that knowledge to the bizarre situations that happen all too often in buildings was somehow passed from Corbett to the rest of us taking the class.  Granted, I’ve never tried learning building science from someone else.  But I suspect that Corbett’s clear presentation style and mastery of the the topics he teaches would be hard to match, let alone beat. 

And he doesn’t let knowledge stand in the way of understanding.  Our field “training audits” were an excellent counterpoint to the classroom presentations, and even though I’ve been doing exactly this kind of audit for over a year with him, it felt entirely different to be in the driver’s seat during  that process.  Balancing the time it takes to do a focused inspection with combustion safety testing and a solid blower door test… it takes great presence of mind, not to mention a head for the details that make or break a safe testing situation.  Like, for example, remembering to turn combustion appliances to pilot before running the blower door.  Simple thing.  Enormous safety ramifications if forgotten.  (And now that I’ve mentioned it here, if I don’t remember to pilot appliances on the written exam, I’ll kick myself!) 

I have to say, I thought I would feel more mastery of building science after passing this exam than I do right now.  But it’s probably for the best.  I wouldn’t want to get sloppy, thinking that with this one certification the learning process is over!  After all, there are building science certifications, conferences, books, research, and experiments being advanced all the time, all over the world.  So I don’t expect that these blog entries will change  much, since I’m still  finding my way in  the expansive world of the building performance  professional.  I’ll still share the little things I discover with you, and try to keep the language as clear & comprehensible as possible.

So I’m looking forward to the new era, but I guess it won’t be all that different from the old one.  Here’s to life, and the constant process of learning that makes it awesome!

*I should also mention that I don’t actually work for Green Dream Group any more, other than writing the occasional blog entry, so I’m not being pressured to say that the class rocked!!  In fact, while working for Green Dream, I wasn’t able to take the field exam with Corbett, thanks to the conflict of interest he had with me as an employee that he wanted to see certified.  In case you’re curious, I now work at CNT Energy, as part of their “Energy Savers” team, where the focus is mostly on reducing utility bills for multifamily buildings.  So drop me a line if you own one: llittle at cntenergy dot org.  Looking forward!

Home Killer IV is:  Indoor Air Quality (IAQ).

Surprised?  Don’t be.  Statistics from the EPA indicate that most Americans spend over 90% of their time indoors, breathing air flavored by whatever the building is full of.  And most of those flavors aren’t exactly good for you.  The LEED (Leadership in Energy and Environmental Design) rating system gives points to homes and commercial buildings that use materials known to off-gas smaller amounts of volatile organic compounds, or VOCs.  But, even though some may be carcinogenic, VOCs aren’t anywhere near the worst of it.   The U.S. EPA website has a more complete list of sources of poor indoor air quality, including radon, tobacco smoke, mold & moisture, and carbon monoxide:  http://www.epa.gov/iaq/index.html 

Carbon monoxide is the one IAQ threat that’s most central to the national standards energy auditors use, and  it’s also responsible for several hundred American deaths each year.   You probably know that carbon monoxide is produced from incomplete combustion of fuels, including natural gas.  It follows that the places to watch out for high levels of CO are near the oven, furnace, boiler, and water heater, or in your garage (especially attached garages).  Because it’s produced along with heat, CO tends to rise at first, but over time it will mix with the air in a room fairly uniformly.  Standards vary on what a safe level of exposure to carbon monoxide is.  BPI (the Building Performance Institute) allows exhaust concentrations of CO to reach 35 ppm before recommending repair to the appliance being tested.

Normally, any carbon monoxide produced by combustion-powered appliances is vented directly to outside, so it’s absolutely no problem inside a house.  Problems only arise when something is wrong, which we see far too often for comfort.  Simple things, like closing off the leaky vent above an old oven, can elevate indoor CO levels in a home far above what’s considered safe, even if it seems to be a good idea and makes your kitchen warmer.  Running a ventless gas heater or fireplace indoors is never a good idea; remember that ‘ventless’ means you’re breathing the byproducts of that combustion!  And there are many more complicated ways for combustion to go wrong, though I won’t get too far into them here.

One of the places dangerous mistakes are made is in the area around your combustion appliances, creatively named the “Combustion Appliance Zone”, or CAZ.  Newer appliances may be power-vented, or have a draft inducer which effectively forces them to properly vent gases to outside.  But many more appliances depend on an adequate air supply to work the way they were designed to.  If you have both a furnace and a water heater together in a small, enclosed CAZ with only a few vents, take a second to imagine what could happen when both machines are running.  The furnace is a powerful beast, pulling air to itself with a fan, making sure  it combusts efficiently.  But the water heater isn’t as strong.  It tries to pull air in, it tries to put its fumes out the right pipe, but if there’s not enough air in the CAZ to go around, the furnace may end up sucking combustion gases back down the water heater’s exhaust flue to feed itself.  That doesn’t bode well for anyone.  It’s still possible, even under those conditions, that there won’t be dangerous levels of carbon monoxide in your  house - the water heater might only be producing a few ppm.  But that doesn’t mean it will always be safe, and where your family’s concerned, safe is the only acceptable solution.

Thus ends the exciting Home Killers series!  Post a comment, ask a question, leave a story, argue a point - make sure you understand how  these home killers will try to get to you, so they never get that chance.

Like heatflow & airflow...

Home Killer II (Heatflow) and Home Killer III (Airflow) are best pals: they work intimately on all kinds of fronts.  Heatflow is one of the factors that determines the direction of air movement, along with wind outside, or the air movement induced by forced-air heating systems.  Airflow isn’t slowed by fiberglass insulation like heatflow is;  it can only be stopped by an “air barrier” like dense-pack cellulose or closed cell sprayfoam.  Confusing airflow and heat barriers leads to confused houses, which kills your wallet faster than anything else, both in utility bills and in the costs of construction.

Conditioned Space or Not?

Ideally, the pressure and heat boundaries should be in the same place in your house.  Your house gets confused when that isn’t the case, the same way you’d get confused if you realized you had three arms, but couldn’t feel one of them.  Examples of places where heat & pressure boundaries get confused: garages, crawl spaces, partially conditioned areas, and the areas around vaulted ceilings.  I saw one house recently where workers had used more than twice as many materials as they needed to insulate the short side attics below the vaulted ceilings.  Not only was that space insulated at the roof and the exterior wall, which by itself would have achieved the same results; there was also insulation against the interior wall, the floor, and the access hatch.  Ask yourself this:  If there was insulation and air-sealing at the roof, what was all that extra stuff on the interior walls and access hatch insulating against? 

Where Air Escapes

Let’s take another look at how airflow and heatflow work together.  The last entry explained what stack effect is: here’s another piece of how it works.  Average houses in the Midwest can have anywhere from 2 to 5 square feet of what amounts to holes in their envelope, spread out in the form of cracks, gaps, and joints across their entire surface.  Gaps located in the upper area of the house, where buoyant warm air wants to go, let already-heated air slip right out into the world.  The gaps in the lower reaches of the house allow cold air from outside to seep in to replace the air that’s escaping up above. 

Somewhere in your house, there’s a level where the air inside isn’t trying to get out, and the air outside isn’t trying to get in - where pressures are equal inside and outside - creatively named the neutral pressure plane.  That’s actually one of the reasons it’s so important to use a blower door when testing for air leakage in homes.  Because pressure relationships dictate that air seeps in where the pressure is lowest (code for the basement or lowest floor) an infrared scan without a blower door would show lots of leakage from outside in a basement, and no leakage at all on the upper floors.  Believing that infrared scan would be a huge mistake; it would result in advice that’s the opposite of what we usually give.  Sealing and insulating the holes in your upper floors, where air’s always trying to escape, is the best way to slow down stack effect, thereby slowing down the rate at which you pour money into your utility bills.

Stay tuned next week for the final installment of Home Killers.  Next time, it’s personal!

Part II: Heatflow.

Where moisture can literally destroy your building, heatflow is what destroys your pocketbook. 

Let’s start with stack effect.  Stack effect is just a name for patterns of heatflow in buildings, which happen because heat rises.  Basically, it means that hot air will always try to move upward in your home, and cool air will always sink.  In a climate like ours, where most of our energy costs go for heating, that means that the top of the house is where most of our dollars are leaking out.

Radiative Heat Loss

 Here’s another interesting side of heatflow.  You remember in high school science classes, where you learned about conduction, convection, and radiation?  Well, here they come again!  Heat can escape your building envelope by any of those means.  Conductive heat loss could occur through exposed, uninsulated ductwork in your attic, or through any substance contacting both warm and cold air.  Convective heat loss is what the stack effect describes, with nice warm air leaking through holes in the top of the structure.  Radiative heat loss is less of a money sink for homes, but describes the fact that the house will radiate warmth as long as it is warmer than the surrounding air.

Measuring heatflow can be revealing, too.  The units in which heatflow is measured are Btus (British thermal units).  At a 1° temperature difference, one Btu passes through material with a U-value (heat resistance) of 1.0 in exactly 1 hour.  What’s interesting about this is that it shows you exactly where the most important areas of heat loss could be in your home.  High temperature differences coupled with low resistance to heatflow - does that sound like ductwork in your attic to you?  If you want to play around with this, the equation is:

Btus = U-value x Area x Temperature Difference x Time elapsed

Insulation, especially at the top of a house, does a huge amount to slow heatflow

If you want the summary, here it is:  Make sure the warmest, most conductive areas of your home are well-insulated!  Those areas are your ducts, pipes (for water heaters or boilers), and the ceiling plane of the uppermost floor in your home.  Pay especial attention to insulating when those ducts or pipes are on the outside of existing insulation, or run through exterior walls.

Stay tuned to learn about 2 more home killers…

This is NOT home killer #1.

No, this isn’t about murder (it’s a family-friendly blog, come on!).   This home killer is more insidious than that, and much more common… 

Home Killer I: Moisture

Moisture will destroy a building faster and more effectively than any other force - except a natural disaster.  Unfortunately, it’s necessary for our comfort that the air in our homes have some moisture in it - usually between 30 and 50% humidity.  Now, if every building was perfectly constructed, with adequate insulation and well-sealed cavities, that amount of moisture would be no problem at all for most buildings.  It’s when moisture is paired with your average home, with confused spaces, and insulation that’s too old or too thin, that moisture can develop into a real problem.

Psychrometric Chart

There’s a ridiculously complicated chart that’s supposed to illuminate the amount of moisture air can hold at different temperatures, called a psychrometric chart.   (Feel free to see if you can figure out how to read it!)  Broken down into its simplest terms, the chart shows that cooler air holds less moisture.  Where 95°F air holds 8 units of moisture, 72°F air holds just 4 units, and air that’s 50°F holds only 2 units.  Air that’s 32°F holds a measly 1 unit of moisture.  So where do houses come into this equation? 

Warm, moist air...

Imagine you have a nice warm house, with toasty, moist, 72°F air inside.  You’ve just taken a shower, so that air is saturated with moisture (4 units).  Your bathroom happens to be at a corner of your house, and it’s always a little chilly in there.  Maybe it’s an old home, without enough insulation in the walls, and not very well sealed.  So what happens when your nice, warm, moist shower air contacts the cold walls of the room?  You can probably guess: condensation happens.  And if it’s a really cold day, say 32°F, three-quarters of the moisture in that inside air will be dumped somewhere between your bathroom wall and the outside of the house. 

Luckily, building materials are able to absorb a fair amount of water.  But over time, this kind of moist air escaping can literally destroy a house from the inside, not to mention the air leakage inflating energy costs every day you live there. 

Don’t fall prey to the home killers.  There are three more to come….

After we sent out our May ‘mythbuster’ discount announcement last week, we realized how easy it can be to misunderstand general statements - about anything, really, but in this case about what it means for an energy audit to work or not.  There are some serious misunderstandings out there, and it’s important to address them head-on.  So here I go.  I’ll try to give a clear & complete explanation, but if anything still doesn’t make sense or if you disagree, please leave a comment and I’ll do my best to address your questions/issues.

First, let’s make a distinction between types of energy auditors, because that’s where a lot of the confusion is coming from.  What you want in an energy auditor is someone who’s been extensively trained in diagnosing whole-building energy problems, either by RESNET or BPI, in the four broad areas of:

Pressure patterns within homes

1) pressure (where air escapes),

2) heat flow (where heat escapes),

3) moisture, and

4) air quality.

And how do auditors diagnose problems in these four areas?  Read on.

* * * *

WHAT  TO  LOOK  FOR  FROM  YOUR  ENERGY  AUDITOR

The diagnostic testing your energy auditor conducts should include all of the following tests - possibly more - none of which depend on outdoor temperature.

1) Complete visual inspection.  Utilizes the energy auditor’s background & training to pick out potential problem areas down the road, in all 4 categories above.

2) A blower door test, preferably combined with zonal pressure testing, to pinpoint air leakage, which is the biggest opportunity for savings in most homes.  These two tests measure the amount of air leakage from the house, in total, and in terms of specific rooms.  Layering on smoke testing identifies air leakage with even more particularity.  Infrared imaging makes these results more tangible to homeowners, and provides an easy way to communicate precisely where problem areas are, but written reports work just as well.

3) Combustion safety testing.  Depends on pressure systems and sources of combustion gases inside the house; has nothing to do with outdoor temperature, and everything to do with air quality and health.

4) Preferable to include utility bill analysis and/or energy modeling, to see how your home performs over time, and verify the issues identified during the testing process.

The tools used for this process include (but aren’t limited to) a blower door, manometer, combustion analyzer, combustible gas sniffer, moisture detector, infrared camera, safety equipment, anemometer, calculator, and training.

* * * *

You can find the official listing of certified energy auditors online at the Illinois Association of Energy Raters’ website: www.ilenergyraters.org.  Every auditor on that list, provided they’re using the training they received, will agree that temperature is not a significant factor in energy auditing with modern tools - with one exception.

One of our IR photos, with a 4-degree range

The only part of a professional energy audit that has any relationship to temperature is infrared or thermal imaging.  Here, it’s important to understand precisely what infrared imaging is used for, and how it’s changed over the past 20 years.  Modern infrared cameras detect tiny temperature differentials, and any temperature difference of over 5°F will generate a clear picture on their screen.  Older infrared cameras (from the 1990s) were not that precise, it’s true.

Innovative use of Infrared Camera

But the key point here is that the infrared camera and its pictures are used mainly as illustrations for homeowners, NOT for diagnosing problems with your building.  Let me rephrase: it’s entirely feasible to conduct an energy audit with no infrared camera.  (It means more documentation by writing, and less fun, but it’s feasible.)  But if, like many homeowners, you’re excited to see those infrared images of your home, all you have to do is either 1) kick on your heat or A/C for a couple of hours before your auditors show up, to get that 5°F difference, or 2) schedule your audit for the time of day when the forecast is most different from the temperature inside your home.

The upshot is that only inexperienced or poorly trained energy auditors, especially those who rely on the infrared camera for more than it was intended to do, have a problem getting accurate results in the summer.  But you shouldn’t hire them anyway, since they don’t have the tools or the expertise needed to give you sound information about your home.

Again, it’s like going to a doctor.  You’d never go to a gastroenterologist who could only diagnose what was wrong with your stomach right after you’d eaten.  You’d wonder why they couldn’t figure out what was going on in your body any time of day, since if the problem is consistent, it probably isn’t the food, but the way your body handles it.  Energy auditing is a much younger field than medicine, and many of the tools and testing techniques used for it are unfamiliar and new.  (Some are just weird.)  But that’s not a reason to rely on old information, or to doubt that the newer methods and tools work.  They work for businesses around the world, doing exactly this kind of testing.  They work for weatherization programs designed to reduce utility bills for those who can least afford them.  They worked for the 80+ clients we audited last summer.  They’ll work just as well this summer, for you or your neighbors.

And just so you know, that May special is still available.

 The funny thing is, it feels like we’re doing a lot of educating these days.  And so is every other home energy efficiency company - the ones that last, at any rate.  In the past month alone, we’ve aired our first TV commercials ( http://www.youtube.com/watch?v=682w94UGkGU ) about home energy auditing, presented at a conference at the Wisconsin Dells, and completed another 6-day training for aspiring energy auditors, not to mention attending the national RESNET conference in North Carolina!  And while it makes sense that there’s a huge information gap to fill with any new industry, it’s surprising how many educated, environmentally aware citizens still have no idea that an energy audit helps them identify ways to save money and energy in the long term. 

There are couple of great ways anyone can start filling that information gap.  One is to check on the website for the U.S. Department of Energy (DOE): www.energysavers.gov.   Front & center, in big letters: Start with an Energy Audit - and the next page goes on to show you how to do an informal energy walkthrough yourself, or how to hire a nationally certified professional for an audit.   Alternatively, you could visit our own Home Improvement Calculator at www.greendreamgroup.com/resources/home-improvement-calculator, which estimates the energy savings you could expect from a house of your general type and condition, provided the repairs are done right. 

But energy auditing is important enough to warrant more than this kind of person-by-person research.  The specific figures vary, but it’s clear that buildings, residential and commercial, represent a significant proportion of the energy used in this country - approximately 40% of the total according to some sources.  If energy audits and related work can reduce energy use by up to 20% (a conservative estimate from CEDA - other programs claim up to 30% reductions), I’m at a loss to explain why there hasn’t been an enormous push towards energy auditing by consumers, if not by the government.  Where’s the missing link?

Thoughts?  Insights? I’d love to hear from you!

And now for something completely different - a sampling of the amazing vendors at the Wilmette Green Fair!

Outdoor Adventure companies, including Northwest Passage (www.nwpassage.com) and Women’s Time Out (www.womenstimeout.com)

Green Lawn Care companies, including Clean Air Lawn Care ( www.cleanairlawncare.com/locations.html#IL )

I-Go Car-Sharing (www.igocars.org - Corbett & Grace are on their front page!)

Divine Pastry and their delicious organic cupcakes! (Sharon Ponton - owner/baker, 847-772-7581)

Get Dwell, Wilmette’s Handyman ( http://getdwell.com )

Solar Service ( www.solarserviceinc.com )

* Many thanks to Go Green Wilmette (www.gogreenwilmette.org), the driving force behind the event, and their many dedicated volunteers! *

Our ad reminds you that, thankfully, you don’t have to know everything to be able to make good choices about reducing home energy use — that’s our job!  All you have to do is take that key first step of getting an energy audit.  From there on, our diagnostic tests and clear recommendations help you every step of the way towards achieving “more comfort, lower costs, better life.”

We’re hoping our ad strikes home for watchers of HGTV, TLC, and The Weather Channel.  It’s also available on our Youtube channel for easy online viewing.  Take a minute - literally - to check it out!  I just did, and I’ll be showing it to my husband when he gets home… did I mention it’s funny, too?!?

Here it is:  http://www.youtube.com/watch?v=682w94UGkGU

P.S.  If you know of another TV ad for home energy auditing, we’d love to hear about it - so far we’ve found not a one.

Home Energy Use by Cost

To begin with, let’s take a look at how energy use in the average home breaks down by cost.  The Energy Information Administration (EIA) numbers show space heating (and cooling) together making up around 43% of your energy bill, with water heating as another 12%.  Appliances and lighting use around 37% of your energy bill.  The remaining 8% varies from home to home.  Bear in mind that if your average yearly costs are very different from these averages, you’ll be able to save more on whatever portion of your bill is larger.  More information is available at: http://www1.eere.energy.gov/consumer/tips/home_energy.html

So what are the best ways to save on electricity use in your home?  There are a couple of ways to answer that.  The most straightforward answer is to minimize your use of anything that requires electricity - refrigerators, computers, A/C, lighting, plug-in hybrid cars, you name it.  That could mean getting rid of a second refrigerator, making sure to always turn appliances off - or better, unplug them - or turning off lights when you’re not in a room.  You could go all out with this strategy; for example, I’d like to stop using the refrigerator entirely.  A couple years ago, I lived for 6 months without a fridge - drinking soy milk instead of cow’s milk, making no more than weekly trips to the grocery store, eating almost no meat - and it was surprisingly easy to pull off.  But I haven’t convinced my current roommates that it would be worth it yet… which may have something to do with our shared love of ice cream. 

There are also a variety of ways to reduce your energy use without going all-out down the conservation road.  These tend to get the most press, because they allow you to maintain the same lifestyle and still reduce your energy usage.  Two of the most popular of these solutions are switching to compact fluorescents (CFLs) and using power strips to turn off appliances when they’re not in use.  CFLs use 1/5 as much energy as incandescent bulbs to produce the same amount of light (measured in lumens), so if you used CFLs exclusively, you could cut your total energy use by as much as 9%.*  Power strips are good for those energy suckers that use energy even when they’re turned off - up to 10% of the amount you spend on electricity could be going to those greedy machines.  You don’t need a power strip to turn off your appliances, of course, but it is nice to only have a couple of switches to worry about, instead of a whole houseful of electronics.

One problem with all of this is that using less energy over the long run so often requires buying something new - light bulbs, appliances, one of those kill-a-watt meters that helps you measure energy flow to a device.  I haven’t found a lifecycle analysis yet for CFLs that includes the impact of manufacturing & transporting them all over the world, let alone the additional cost of returning them to manufacturers for safe disposal, or the comparison of those costs to the ones incurred by reasonable alternatives.

The approach I like to take to saving electricity at home is a comfortable blend of conservation (laundry once every 3 weeks, low temperature settings on the furnace & water heater) with convenience (CFLs & power strips).  The best way to find out what you’re comfortable with is just to take the plunge, and try out a few different options.  Who knows - maybe getting rid of the fridge will be part of the lifestyle change that makes you happier & more fulfilled.  And if, like my household, you just can’t imagine a house without ice cream, remember that there are plenty of other ways to get your ice cream fix than keeping it in the fridge for days.  And there are plenty of other ways to save energy, too!

If you’ve got a favorite strategy or action that helps household energy conservation, I’d love to hear about it!   Drop me a comment, and I’ll get back to you as soon as I can.  And enjoy your experiments in saving energy!

*Though it’s most effective to install CFLs in high-use areas, like living rooms, rather than closets or hallways.  Their lifespan is limited mostly by how often they’re turned on & off, so it’s more cost-effective in the long term to use them where they’ll be on for more than 5-10 minutes at a stretch.

The To-Do List.

To begin with, I should let you know that my current rental was built back in the 1870s.  I have no idea what kind of insulation, if any, is in the walls.  Sticking my head up into the attic was one of the most frightening things I’ve ever done - the insulation was black and stringy, and the way it was hanging from the rafters made it look like snakes, or bats - and I could feel dust seeping into my lungs every second I tried to look around.  There are a couple of rooms that never seem to get warmer than 55 in the winter, even when the thermostat is set to 67. 

Basically, this house has more than its share of challenges… and we’re paying for heat.  We haven’t taken a close enough look at how our heating bills compare to heating degree days (HDD), so I can’t tell you with any confidence that some particular combination of strategies saved me so much on my gas bills.  I wish I could.  I’m definitely more comfortable in my bedroom now, where the window over the bed has caulk around the edges and is covered in plastic.  But hard evidence aside, if you’re interested in spending a little less on gas, or just feeling more comfortable in your home, these suggestions will help.  Here’s a short list of DIY upgrades that should save you money on heating in the short run.  We’ve got some great videos on the main page illustrating precisely how to install these upgrades the right way: www.GreenDreamGroup.com/resources/diyvideo

Some serious AC action

- take room A/C units out of the windows in winter - leaving them in is like leaving a window open all winter, which doesn’t make much sense.  If your A/C is permanently installed, do your best to cover it up, inside and out, with plastic and/or insulating blankets, rigid foamboard, or anything to slow air escaping.  This is a huge source of heat loss!

- weatherstrip around doors & locking windows; if there’s no lock, you won’t be able to keep the window pressed against the weatherstripping firmly enough to reap any benefits.

- caulk or sprayfoam around visible holes - door frames, windows, dryer vents, electrical or plumbing penetrations.  (Finding these holes can be a fun activity to tackle with your kids.)

- cover the windows with plastic: most effective if you have single-paned windows, like I do.  With double- or triple-paned windows, most of the leakage tends to occur around the edge of the framing, so plastic won’t be as effective.

- caulk behind baseboards - they’re often covering up the seams of a house, which is exactly where air tends to leak in. 

- Finally, one thing NOT to do: if you have a gas oven with an exhaust fan over it, DO NOT stuff insulation into the fan and cover it with plastic!  The reason the exhaust fan  is there is because the fumes from your oven could be dangerous to have in your breathing space.  Even having a carbon monoxide detector in the same room isn’t the same as standing over the oven for a couple of hours - the concentration of CO is much higher closer to the source.  If you feel cold air coming in when the fan’s not in use, try checking the outside of the house - make sure the flap on the other end of the exhaust vent closes snugly, or install a new one.

Now that winter this year is almost over, it may not make sense to complete everything on that list.  Some of the upgrades last a long time, and some need to be replaced every year, like window plastic.  Use your best judgment, check our online videos for tips, and let us know any other ideas you’ve heard or are using.  And have fun!