The Dilemma: Solar Panels (Sexy!) Or External Wall Insulation (Not Just Unsexy, But Invisible)

[hatrack]

I'm a bit of a gadget man. So in my bid to give my house a green makeover, I've been reading around the subject of renewable technologies. I had thought that the "silver bullet" to eco heating was a combination of a heat pump and solar photovoltaic panels (to offset the cost of running the pump). One unit of energy to get four back seems a good proposition, until you start to dig into it further.

By my calculations, heat pumps cost a lot of money. I'm not saying they should be dismissed as an option, but suggest they need careful thought. Air source heat pumps are another option and have a comparatively affordable upfront price, but they usually have lower efficiency and therefore look as if they'll have higher running costs.

So, where do you start if you want to eco renovate? Clearly I need a cunningly prioritised plan of action, and after reading ECO Refurbishment by Peter Smith and the Green Building Bible, the obvious answer is to focus on reducing our energy use rather than jumping to creating energy.

I'm currently learning as much as I can on External Wall Insulation (EWI) and am about to attend a day's course on the subject at insulation experts Weber. One other source of advice on insulation is T-Zero, a web-based tool designed to help homeowners learn what green improvements they can make to their house. It looks as if it has potential, but it doesn't seem to offer EWI as an option.

EDIT

http://www.guardian.co.uk/environment/ethicallivingblog/2009/apr/27/green-your-home-external-wall-insulation

[Grey]

1. Passive Solar,

Heat sinks. Insulation, not just walls but ceilings as well, up to R-40. Talk to the people over in the Frugal Forum.
There are any number of things you can do.

[Ready4Change]

2. Always start with insulation.

It provides the biggest bang for buck. Further, it will multiply the effects of whatever you do next.

[XemaSab]

3. Oh, you're a *gadget* man?

;)

[hatrack]

8. Well, that would be the author, not me . . .

As it turned out the first thing we went for in our house was insulation.

And who knew? Our furnace guy said that whoever sealed the sill plate did "one helluva job" - and that whoever would be me, thank you very much!

[htuttle]

4. Always insulate first

If you could insulate well enough to allow you to heat your house with a 9V battery, it would become irrelevant how you came up with the power.

[Nederland]

17. Sure...

...provided you're willing to get sick from lack of sunlight and fresh air. :)

[kristopher]

5. The article mis-states the energy payback of solar PV

"One unit of energy to get four back seems a good proposition, until you start to dig into it further.

From NREL Report No. NREL/FS-520-24619 January 2004

"Energy Payback: Clean Energy from PV
Producing electricity with photovoltaics (PV) emits no pollution, produces no greenhouse gases,
and uses no finite fossil fuel resources. These are great environmental benefits, but just as we say
that it takes money to make money, it also takes energy to save energy. This concept is captured by
the term “energy payback,” or how long a PV system must operate to recover the energy—and
associated generation of pollution and CO2—that went into making the system in the first place.
Energy payback estimates for rooftop PV systems boil down to 4, 3, 2, and 1 years: 4 years for
systems using current multicrystalline-silicon PV modules, 3 years for current thin-film modules,
2 years for future multicrystalline modules, and 1 year for future thin-film modules. With energy
paybacks of 1–4 years and assumed life expectancies of 30 years, 87% to 97% of the energy that
PV systems generate will be free of pollution, greenhouse gases, and depletion of resources. Let’s
take a look at how the 4-3-2-1 paybacks were estimated for current and future PV systems..."

Worst case five years ago 1:7.5

[Fledermaus]

16. Your funny. The less you understand the more noise you make.

The poster was obviously talking about heat pumps.

Heat pump performance

The heat delivered by a heat pump is theoretically the sum of the heat extracted from the heat source and the energy needed to drive the cycle. The steady-state performance of an electric compression heat pump at a given set of temperature conditions is referred to as the coefficient of performance (COP). It is defined as the ratio of heat delivered by the heat pump and the electricity supplied to the compressor.


http://www.heatpumpcentre.org/About_heat_pumps/HP_performance.asp

Typical COP for electric compression heat pump is 2.5 to 5. Or, as the poster commented, put one unit of energy in and get four out.

[kristopher]

18. NO.

The poster wasn't "obviously" talking about the heat pump.
"I had thought that the "silver bullet" to eco heating was a combination of a heat pump and solar photovoltaic panels (to offset the cost of running the pump). One unit of energy to get four back seems a good proposition, until you start to dig into it further."

It is ambiguous at best. The writer was talking specifically about a heat pump in conjunction with PV. However even if you're correct as to the intended meaning, it is still an incorrect assessment since the energy benefits of the PV are not being considered at all.

[Fledermaus]

19. You think so?

[TreasonousBastard]

6. What do you do about the roof? That's...

where you can have a real heat loss. And little things like uninsulated switchplates, gaps in doors and around windows...

But, the basic question is where do you live that it gets so cold you need all this stuff?

Next question is after you added up all the degree days and plugged them into a spreadsheet getting your BTU requirements and dealing with the losses, do you need anything much at all. Or will a heat pump backed up with a fireplace or Franklin stove do the job?

My plan, if I ever get to do it, is either a major earth berm over everything but the south facing wall of the house or possibly even most of the living spaces completely underground. Very little heat or AC needed then.

[Nihil]

7. Always insulate first.

Roof space, cavity walls, windows, draughtproofing, hot water tank.

After doing all of the above, solar hot water is the next best bet
(at least it was for me).

Solar PV might be considered "sexy" but there are a lot of things
higher on the list than that for most homes (lighting, Energy Star
appliances, ...) and these will all be cheaper + faster return on
investment than the comparatively massive capital expenditure on PV.

:hi:

(ETA: As the author is in the UK, there are also grants to help out
with loft insulation and cavity wall insulation - even less excuse
not to do them!)

[Bushfire]

20. We had our house insulated last fall

and have noticed a substantial improvement in our comfort level, and heating bills. We had an energy audit done first with a blower door test, and thermal imagery to give a blueprint for where we needed the insulation most (pretty much everywhere) in our 1920's single family house. We went with a company that specializes in blown-in cellulose insulation. Overall investment about $4000.00. Rebate from utility funded energy program $750.00. Winter heating bills noticeably cheaper, and should pay itself off in 5 to 10 years depending on price of natural gas plus the weather. Added bonus to insulation work, outside noise (traffic) much quieter. Should any have questions, feel free to let me know. We replaced an original wood door on the side of the house this spring that had plenty of drafts with an Energy Star rated door as well.

[Nihil]

21. Interesting ...

... I've never heard of an "Energy Star rated door" ... thanks!
:hi:

[AZCat]

25. The "Energy Star" program has expanded quite a bit.

They have a pretty good website. You should take a look --> www.energystar.gov

[muriel_volestrangler]

22. He already has cavity wall insulation

and some roof insulation - and grants for further insulation are not universally available in the UK (it depends on your financial circumstances, what insulation you already have, how easy it would be to do (someone came to give me an estimate, took one look at my loft space, said that health and safety regulations wouldn't allow anyone to be employed to work in such a small space, and left)).

His blog is here; here's an entry which talks about some options he's considering, in which he says his wall cavities are already insulated.

[Nihil]

23. Ah ... OK ....

I didn't get that from the article - only saw that he had flagged
"external wall to be insulated" so thought it would be worth
mentioning.

:hi:

[hunter]

9. I keep thinking I'll get around to the solar electric part...

... but when I run the numbers I never do.

We live in a very mild climate. It was pretty easy to get to a place where the furnace that came with our house was grotesquely oversized and wasteful. Good bye furnace. I'm not sure what I'm going to do with it -- if I break it down and recycle the parts that's one less 80% efficient furnace in the world, if I give it away that's somebody else feeding it natural gas.

I now think simplification is the very best way to solve energy problems. Instead of using complicated gadgets like residential solar electric panels, we can simply build and retrofit houses so they don't need central heating or cooling, and build or retrofit communities so people don't need cars.

There's no reason to use large amounts of energy at home, although I still have a couple of "gadgety" ideas floating around in my head -- one of which is to divert hot water from the showers, dishwasher, and washing machine to an indoor tank which would then heat the house in the winter. It might also be part of a graywater system, but even that point is moot in my community because we have a very modern wastewater recycling system.

[kristopher]

10. How does that logic work?

Redesigning our living spaces to consume a fraction of current usage? That's the plan and it is a sensible move. But how does that remove the benefit of using distributed PV to meet the bulk of our remaining usage?

And how do you figure that a home PV system is "a complicated gadget" when the alternative is large scale fossil or, even worse, nuclear?
Edited to add: By "worse" I'm referring strictly to degree of complexity.

[hunter]

11. Most power is used by commerce and industry.

Residential power use might be reduced to something negligible in comparison to that, in which case those commercial entities ought to be carrying the major responsibility for the energy infrastructure. Let them finance and install solar panels on their rooftops or over their parking lots. Then, if I don't want to finance any expansions or improvements of the energy infrastructure I can simply stop buying things that use a lot of energy in their manufacture or distribution.

The way things are now residential users are held hostage by commercial users whenever there are real or perceived power shortages. It's never been about keeping the lights in our own homes on, it's always been about keeping the lights at Wal-Mart on. If I put a grid intertie system on my own house I'm buying into that energy network, and if I'm buying solar, I'm financing much more of that network than industry and commerce are willing to put into it.

[kristopher]

12. "Let them finance and install solar panels..."

That is precisely what is happening. The entire concept of distributed generation is that each energy user is more immediately involved in the production/consumption process. In fact, the rollout for PV is primarily being driven by commercial entities using their rooftop space ( http://www.solyndra.com/ ) and utilities contracting to meet peak demand. This is having the expected result of driving prices down pretty fast. Combine that with the move to EVs and the effect mass production will have on the price of battery storage and in the not too distant future you have the makings of a workable and affordable system for individuals.

To me, your perspective seems somewhat overly focused on evaluating the entire energy landscape by your immediate personal economic welfare.

[phantom power]

13. Efficiency! Whiskey! Sexy!

[kestrel91316]

14. The external wall insulation I put in the hallway of my office is plenty visible.

Um, that would be because I STILL haven't got around to getting a sheetrock guy in to give me my wall back, lol.

[Fledermaus]

15. Insulate, you will get your money back.

[ConcernedCanuk]

24. I'd go for the solar panels - emergency hydro for power outages

.
.
.

My main need/concern for electricity is food preservation.

The house in the article has a wood-stove -

heat problem solved as long as you have a reasonably priced source of firewood.

With an independent source of hydro(solar with batteries/inverter) - one can weather power outages with little disruption or concern.

I have a neighbor, yes, in Northern Ontario that is totally solar, no hydro pole feeds their property.

When there is a power outage, they don't know it unless someone phones them!

Now THAT is why I would go for the solar option first.

Our power outages are getting more frequent, and longer in duration.

Solar photo-voltaic panels - THAT's where I'd be putting my first $$$