Chimneys Are A No-No

Wood burning masonry fireplaces, while they used to be desirable in homes as recently as the 20th century, are an energy efficiency disaster.  (Direct vent woodstoves are usually OK)

Gas fireplaces can be less of a problem, but they are usually vented with a metal pipe of some sort.

Therefore, every new chimney you've seen in the past 20 years is a FAKE chimney, stuck on by an architect or home designer who thinks it's necessary to "make a house look like a home" or whatever.

Stay away from fake and real chimneys because they hurt the integrity of your insulation and air sealing layers, and compromise the durability of your roof.  In my ownership and maintenance of 200 or so homes in the Denver area, chimneys are the most common location for roof leaks.

Off Peak Cooling in Colorado

As you study the costs of electricity generation, you find out that Xcel's cost go up sharply during hot summer afternoons.  Back in the days of off-peak, or TOU, rates, PSCO tried to pass the extra cost on to the customers.  This pricing scenario has faded out over the years, but may come back.

Evaporative cooling works best at night, so you can accomplish off peak cooling by overcooling your house at night  and in the morning.  The cheaper coolers hardly work with a daytime temperature above 86F anyway.  The thermal mass of your house will then let you coast through the afternoon without using air conditioning at expensive rates.

Green Backup Power

After Hurricane Sandy, having a backup source of power for your home has become more important to some people.  Using a gas generator is one option, and they are very economical to buy, but not necessarily to run.  After Sandy, it was tough to find gasoline.  Another option is to have a permanently installed natural gas generator, but this isn't a good option in an all-electric home.

If a lengthy power outage ever hits Denver, those of us with large PV systems will be kicking ourselves for not installing an easy way to go off grid.  You see, all the PV systems you see on private houses currently DO NOT WORK if the grid is down.  The average refrigerator has $200-$300 worth of food in it.   I'm allergic to most candles, and they are a great way to burn your house down, so backup electricity would be nice.

I'm sure that the big power purchase agreement providers, SunRun and Solar City, are working on this, and I'll post the answer here when I get it.

EDIT 3/18/13:  The inverter company, SMA, will be releasing a new inverter that has this functionality.  It will have "an emergency power supply to provide daytime power in case of a grid outage".
This is expected in 2013, so be sure to request it for your house.
The ultimate system will use your electric vehicle or plug in hybrid for electrical storage and backup power.
R. Carter Scott plans to do this, and I'm sure he'll report more about it.

LED Lighting Innovation?

110v LED light bulbs each contain some circuitry to make them work with 110 volts AC.
LEDs are happier with 24VDC.  LED bulbs also use just a small fraction of the power of incandescent bulbs. That means that the typical 14 gauge wire going to light fixtures will be overkill for LED lighting, and be a big waste of copper.

So, theoretically, lots of money could be saved in new construction if the lighting power and distribution system could be optimized for LEDs.

Lumencache.com proposes to do just that.  This is a great idea, but boy, high volume means everything to low prices.  Trying to change how new homes are wired will be an epic uphill battle against code officials, old building professionals, and timid homebuyers.

Strategies for Using a Photovoltaic System to Achieve Net Zero

We have designed a 1400 square foot 2 bedroom house to build near Platt Park. The levels of energy efficiency are comparable to Passivhaus standards, but our main goal is net zero energy cost.  The only way to achieve this goal is with renewable energy. A photovoltaic (PV) system is the best choice.

Now, we could make some reasonable assumptions about projected energy usage for the house in order to size the PV system.  In reality, it's impossible to predict the actual usage for a house, so let's look at the whole problem for other clues to size the PV system:

1.  The roof size places a practical limit on the system size based on the actual roof size and how much photovoltaics will physically fit on it.

2.  In new construction, Xcel Energy limits the size of your proposed system based on how much energy they think you will use.  They make a very primitive and arbitrary guesstimate, but the good news is that they will let you oversize the system and pay you more than retail for all the energy you collect and put on the grid. Since Xcel pays you retail price for the energy you generate, they get to say what the maximum size is.

3.  For an existing home, Xcel will let you size the system based on your last 12 month's actual energy usage.  They will let you build it 20% larger than that if you really want to (because you're SURE to get an electric car here in the next two years, and you need the extra capacity).  For most homes, the roof will be nowhere large enough to provide all your energy needs with PV

Xcel used to pay a one-time cash rebate on your system as soon as it was installed.  Nowadays, the rebate system is performance-based. Your contract with Xcel simply obligates them to pay you, as the system owner, $0.13 per kwh generated, up to the contract maximum per year for ten years.  The contract maximum is also the expected annual output of your system.  This strategy protects Xcel because if your system doesn't perform as expected, they don't have to pay.  It also gives you a big incentive to get your system functioning properly.

By entering into a typical power purchase agreement (PPA) with a solar leasing company such as Sun Run, you can get in the game immediately with no cash out of pocket

Video: Cold Climate Direct SDHW system with Recirculation Freeze Protection

I've mentioned this system before, and I finally made a video.  Please remember this is the first prototype system, and is intended to be temporary.  (It's ugly.)  Our current thinking is that the system isn't developed enough for general public consumption, but I definitely recommend it for do-it-yourself types in milder climates. It is literally the least expensive and most efficient system with freeze protection possible with off-the-shelf parts.

We've instrumented the prototype system, and are checking all the failure modes this winter and measuring the amount of heat lost due to freeze protection.  The video still raises many questions, so don't hesitate to ask them in the comments section here, or preferably at Youtube.

Smart Light Bulbs?

Phillips has recently introduced their HUE lighting system.   It's a wi-fi based light bulb control system for timing,  brightness and color.

How can you use it around the house to save energy?  Honestly, I can't think of any scenarios that would reap enough savings to justify a $60 bulb.

But in multifamily buildings, there's the hallway lighting to address.  In the middle of the night, the hallways could be dimly lit.  During the day, the lights could be completely off.  This system is competitive with the cost of hardwiring timers and dimmers.   And I've never seen dimmable timers.  You could save at least 30% of your hallway lighting cost.  Still, I'd wait until these bulbs come way down in price.