Central heating: overview and numbers

Here's the last of the central heating info - we haven't had a power bill yet so will update with approximate running costs when we get that, but for now I thought I'd summarise what we think and how much it cost.

The highly attractive heating unit, just after we started the ducting

The system we chose is the Rinnai iHeat. It's a ducted system, so blows warm air into the rooms. The air is warmed by water from the Infinity water heater we installed (which will also eventually serve both bathrooms and the kitchen).

Pros:

• Keeps the whole house warm when we have the system turned on
• Warms the house up pretty quickly (much quicker than a heat pump or fire)
• Cheapest option for whole-house heating
• Ceiling vents are unobtrusive
• Very quiet
• Efficient (and hopefully cheap to run!)

Cons: 

• Blown air is not quite as nice as radiant heat
• Can't control zones separately - one thermostat for the whole house

We have made a few tweaks to improve performance, and have a couple of other things we're planning to do in the longer term as well. 

Behold the button-thing, by which the vents may be adjusted

Firstly, balancing is part of the set up, but basically just means varying how open the vents are. Each vent has a button-thing (technical term) in the middle which allows you to adjust flaps inside the grill. The flaps can be mostly closed (so almost no air flows through) or fully opened (so as much as possible comes in). To balance the system, i.e. try to get all the rooms evenly heated, you start with the rooms furthest away from the heating unit, fully opening their vents, and then work back towards the centre of the house, with the more central vents being progressively more closed. 

Despite balancing, the airflow downstairs isn't as good. There are three ducts for downstairs; one in our son's room; one in our room; and one in the future bathroom. The one in our son's room works pretty well, but is poorly located above the door. Since his door gets closed when he's napping, which is when it most needs to be warm, it works okay, but we'll monitor that for a while and may eventually move the vent. 

Our bedroom is served by a poorly installed piece of flexible ducting, adopted from the HRV. Our room is the least accessible, ducting-wise, so we plan to eventually (before next winter!) get a length of rectangular plastic ducting to replace the dodgy old stuff. Because it's a straight run but we don't have good access between the rafters to smooth out the flexible ducting we think this will make a big difference. 

The bathroom vent is currently capped, because the bathroom doesn't even have walls and we're not really interested in paying to heat the dirt under our house. Once the bathroom has been built and that vent is in action we imagine the downstairs will become a bit more temperate, but in the meantime we've still got a heat pump down there for colder days (it's probably been turned on - briefly - three times in the past two weeks). 

We noticed immediately after it was turned on that the roofspace was very hot when the system was running, and realised that some gaps in the metalwork of the heating unit meant heat was escaping unnecessarily. I rang Rinnai to check if we could stop up these gaps, and they said that was no problem, so long as we used an appropriately heat-rated silicon sealant - so out came the caulk gun and now hopefully we're not leaking money into the attic. ;-) 

Another possible future tweak is the addition of a damper so we could turn off rooms not in use. These can be operated by a wall switch and can close off a branch of the system. The advice on this is a bit conflicting - our gasfitter said the iHeat's computer would shut down if we used one, as it would detect the damper as a blockage in the system, but Rinnai's info says they can be used. We'll see how the running costs look and then potentially do more research on that one.

The position of the thermostat is the subject of some discussion - it's in the warmest area of the house, which is not ideal, but it is conveniently located... So again we're going to wait and see. Installation consisted of poking a bit of cable down the wall and plugging the wall unit into it, so if we decide it would be better somewhere else we just need to fish the cable out and dangle it down a different wall. 

Overall we're very happy - the thermostat is quite programmable, so it turns on before we get up in the morning and turns itself off at bedtime, and we are magically kept warm without even thinking about it. You can easily turn it off if you're leaving when it's programmed to be on, and you can increase the temperature and/or fans temporarily if you're feeling particularly cold. 

And the cost - well, it's a big outlay, yes, but overall not too bad considering the outcome. For us, well worth it. If you're looking for something similar but don't have reticulated gas available in your area I'd encourage you to look into heat pump central heating - slightly more expensive but still a lot more reasonable than a furnace system! 

Costs:

System install (Infinity water heater and iHeat system, including commissioning) - $10,547.88

Extra vents - $184.71

Electrical work - power to the Infinity and iHeat units, decommissioning heat pump - $500 (approx)

RJ45 cable and connector for thermostat - $16.80

Cable ties - $92

Recovered $$$ from sale of both HRVs and one heat pump (less Trademe fees) -  -$1748.27

Central heating installation

Budget: $10,000

Timeframe: 6 weeks (mostly waiting for gas to be hooked up)

Who did the work: Us (4 days), gasfitters (1.5 days), sparkies (half a day)

Actual cost: $9,593.12

Learnings: Installing ducting isn't very hard, though it is a bit unpleasant spending a lot of time crawling around in attics. Pay attention to how things are working after installation as small tweaks can make big improvements in performance and efficiency. 

Keeping warm - the central heating edition

We are a day away from firing up our very own central heating system. It's a very un-Kiwi way of heating a home, but one that we hope will be both comfortable and efficient. I'll come back to how it works for us once it's up and running, but I wanted to share why we've chosen a central heating system instead of say, a heat pump or a fire.

When we moved into our house, it had two heat pumps and two HRV systems - one of each on each level. Both heat pumps did a good job of heating the rooms they were in. Unfortunately, the downstairs one is in our bedroom, which we prefer on the cool side anyway - 16-18 degrees is about right for sleeping, I reckon, so not much heating needed. Upstairs it was in what would have been the dining/living room for the previous owners, but will be dining/kitchen for us. Useful, but it leaves our lounge, the other three bedrooms, two bathrooms and hallway out in the cold.

And as for the HRVs - well, they did remove moisture from the air, but as I've written before, I'm not sold on the benefits of those systems; I prefer to minimise the moisture that ends up in the air and use the high-tech apparatus known to those in the trade as "windows" for ventilation.

We knew we'd have to do something about heating those extra spaces but it wasn't the immediate plan... Until we got into hot water.

Because we're adding a bathroom downstairs we knew we'd need some extra water heating at some stage, and since we're in the midst of relocating the kitchen, which (who knew?) involves plumbing, it made sense to look at water heating now, so that we don't end up running a whole bunch of new pipes and then needing to move them in a year or so.

So we started investigating our options. As well as the water heating, we had three distinct problem zones for heating: our son's downstairs bedroom (which bears the brunt of the bitter southerly, straight off Cook Strait); the new lounge; and the two upstairs bedrooms. We went through a lot of different options, which all had complex costs and benefits associated. So we did what anyone would do; we made a spreadsheet.

All the coolest people run their life with spreadsheets

As you can see, all of the options we came up with were pretty costly. The cheapest option was about $7k, and that didn't serve the whole house very well. The top of the range isn't really shown here because we only looked at cheaper central heating options - I'm sure a radiator system would have taken us well over the $20k mark. 

Having read a bit about it before we got the quote, we had high hopes that the gas central heating system might come in at a reasonable price. It's a newish system (Rinnai iHeat) which works off the Rinnai Infinity water heater, which means the water heating cost is bundled into the total.

Disappointingly, at just shy of $14k it was well over our $10k budget. And then my husband had a stroke of genius: what if we were to run the ducting ourselves? We suggested it to the gasfitter and he agreed that might be a good option. We're grateful that he was pragmatic*, because when the quote came back it was nearly $3k cheaper, which made it make sense for us (not to mention that we do quite enjoy the DIY malarkey and find it more satisfying to be part of the process and understand how it all works).

It's more than we were planning to spend on heating in the short term, but it makes more sense to do it now than having to patch heat pump holes in our freshly painted walls in a year or two - and we should get over $1000 back by selling the heat pumps and HRVs. So net cost should be a smidge under $10,000. 

The moral is: it's expensive, but actually not that crazy if you have several areas in your home that need heating. And for goodness' sake if you're thinking of installing two heat pumps and two HRVs think about whether central heating might make more sense! We feel quite sad that the previous owner spent all that money for very localised comfort when he could have had the whole house toasty.

Have you ever thought about getting central heating? If you have it, how do you find the running costs?



* understandably many tradies don't want DIY wannabes like us doing half the job, lest we try to blame them for our own ineptitude

Money stuff: creating a budget

I highly recommend forming (at least) a rough budget as part of the planning for any project. I'm not sure whether it's my project manager self or my tightwad self which dictates this (perhaps both!) but it's a key step in the planning and can inform decisions further down the track. 

Depending on the project this can be pretty easy, but when we were looking at buying a house that needs an overhaul on pretty much every front, the budget creation got a bit daunting. We went through a few iterations, the first of which was very, very rough. I don't seem to have it any more, but it was something like this: 

• Repiling - $50,000
• Kitchen - $40,000
• Bathroom - $20,000
• Reconfiguration and decor - $20,000
• Total - $130,000

I can't remember if all of the numbers are what we put down initially but they were along those lines - very high level (though I do know that's what I put for repiling because my dad laughed me out of town when I told him, and then it turned out to be only one corner, not actually a pile and only cost about $1000 to fix). 

That was enough for us to know that it would be worth putting in an offer - and it gave us a rough guide as to what the offer should be. This equation is: 

Potential Value - Renovation Cost = Offer Price

Note that we're not looking to make money (though we won't complain if we do!) - we just wanted a) a project; b) a nice family home at the end; and c) not to be throwing money away. If you were trying to do up a house for profit you'd want a significant margin in there as well - though you'd also likely not change some of the things we're changing and therefore you'd spend less. 

Once we'd negotiated and agreed on a price with the vendor, we got a building inspection (actually, we talked one of the companies that had provided the building inspection to an earlier bidder into providing the same report to us for a discounted price, since they didn't have to revisit the property). 

When we had the building report in our hot little hands, we added every defect needing to be addressed to a gigantic list, and assigned costs to each one. 

Most of the numbers are very approximate - generally we put $1000 per day of work (which usually covers some materials as well as labour) unless we had a better idea. 

We also checked the scariest looking problem - cracks in the retaining wall at the back of the house - with an engineer. If that had required work it probably would have been $50k, which would have been a deal-breaker. 

The total (after we'd added renovations, with a bit more detail and verification - i.e. I asked my dad, which is the standard sanity check process around here) came out at $130,120 (that over-estimated pile repair ended up covering a bunch of other remedial jobs). 

This list is now our master to-do list and budget. 

A snippet of our budget / to-do list

Because I like to see how we did on our forecasts (I always liked tests at school, too; weird, I know) our initial estimates (the "Approx cost" column) is now locked down. The grey lines are things we've completed, and as you can see we're not too accurate on the line-by-line - but overall we're still about even. 

(installing the dishwasher actually cost about $40 but it was the same receipt as paint for the kitchen and I'm not that dedicated to separating the costs)

I have also categorised and prioritised each task. This helps us see, for example, all the costs associated with the new kitchen, and how much money we need to have within the next few months for the high priority items, vs in a year or two for the things further down the list. 

It might be a bit over the top but hopefully it means we won't get any nasty surprises - and it is a bit sobering seeing those numbers adding up so it probably makes us a bit more careful too. 

So tell me - how do you plan your budget for projects? Or do you prefer to just do it and hope for the best? ;-)