Renovate your period building in the right order — and stop signing anything blind.
An independent engineer for existing buildings on your side — no commissions, no ties to manufacturers. So that you know what your house needs before you spend money.
Thomas Tergan · Industrial engineer (studying civil engineering)
Initial conversation by video or phone · Site visits in Dresden and the surrounding area on the basis of a quote
- Over 12 years of experience
- Over 50 period-building projects
- Over 100 building owners supported
- DGNB Consultant and Auditor
- Independent no commissions
Three misconceptions that can cost a lot of money in a period building.
You will find them in quotes, in sales pitches and sometimes in well-meant advice. They become expensive when nobody checks them against your own house.
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Misconception 1
“A heat pump won’t work without underfloor heating and a new façade.”
In fact: Often just a few radiators set the temperature for the whole house. More heating surface in exactly those places lowers the flow temperature, without anyone touching the façade. The case of the K. family just below shows what that can look like.
The Renovation Roadmap → -
Misconception 2
“Insulate first, then we’ll see.”
In fact: Most expensive mistakes are not mistakes of material. They are mistakes of sequence. Which measure comes first follows from the fabric of your house — not from a package deal.
Free guide: the order in ten steps → -
Misconception 3
“Polystyrene is the cheap option.”
In fact: What is cheap is the price in the quote. Service life, maintenance, repairability and removal rarely appear there. The German federal building research institute (BBSR) puts the render on the insulation at 45 years and the paint finish at 20. A polystyrene façade needs a maintenance plan.
The Polystyrene Deception →
This is not your specialists’ fault: each of them sees their own part. The signature for the whole is yours.
Calculated first, then cut.
The difference is not the building. It is whether anyone did the calculations beforehand.
The K. family · Quoted
€84,000
For façade, windows and heat pump.
The K. family · Calculated, not estimated
Façade and windows: cut
The K. family had a quote of 84,000 euros for façade, windows and heat pump. The façade and windows were dropped. The heat pump went in, together with two new radiators; including installation and hydraulic balancing, the radiators cost 4,200 euros, and the heat pump is not included in that figure. 55 °C flow temperature, every room warm. A single case from my consulting practice, not a promise for every house.
Sometimes a house does need the major measure. Then it is marked as necessary on the traffic-light list — and you know before you sign.
The Renovation Roadmap works through the case step by step in lesson 1.1 (course in German).
What does your house really need? 20 minutes, by video or phone, free of charge.
Free initial conversation (20 min) →The Renovation Code: fabric first, then the order, then the signature.
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Step 1
Read the fabric
Before anyone plans, the house is understood: what is there, what is damp, what is load-bearing, what is missing from the documents?
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Step 2
Classify the measures
Every planned measure is classified: necessary, advisable, optional or questionable — each with a reason. In the “Kein Groschengrab” guidance, this becomes your traffic-light list of measures.
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Step 3
Set the order
What comes first, what can wait and what depends on what. Only then do individual quotes come into it.
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Step 4
Check the quotes, then award
Is the work fully described? Which assumptions are still open? Where can you see a risk of additional claims? Signing comes afterwards. This is a technical and economic review, not a legal review of the contract.
The guide, the video courses and the one-to-one guidance “Kein Groschengrab” all work on this principle — just at different depths.
Kein GroschengrabTraffic-light list
Every measure with a reason.
- necessary
- advisable
- optional
- questionable
Before you sign
Where do you stand right now?
Not every situation needs the same thing. Choose the route that fits where you are.
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01
“I want to get my bearings first.”
The guide “A Period Building Without the Nightmare” sets out the order of a period-building renovation in ten steps.
Free · PDF · 13 pages · in German
Get the free guide → -
02
“I want to understand it myself.”
Three video courses from practice: The Renovation Roadmap, The Polystyrene Deception and The Renovation Code. You learn at your own pace and decide for yourself.
From 37 € one-off, incl. VAT · in German
To the video courses → -
03
“I have a specific question.”
In the Altbau-Sprechstunde you get concrete answers to your questions — you choose the topic. You send your documents in advance.
60 min by video · €149 incl. VAT · written summary · in German
Book the Altbau-Sprechstunde → -
04
“The quotes are on the table.”
Kein Groschengrab: the 12-week guidance before you award contracts. You don’t need to know everything yourself. You just shouldn’t sign blind any more.
First the free initial conversation, then price and quote · in German
More about the guidance (in German) →
A Period Building Without the Nightmare — The Renovation Code
The exact order of your renovation — so you only pay for what is really necessary and never do anything twice.
- The three measures almost everyone tackles too early — and the condition under which they can be brought forward after all
- The roadmap in ten steps, each with a clear “done only when”
- Ten technical terms from contractors’ quotes, each explained in one sentence
I’m Thomas Tergan.
I have over 12 years of experience in construction consulting, project management and construction cost control, with over 50 period-building projects and over 100 building owners supported. In 2025 I founded Sustainabim in Dresden. My focus is preserving building fabric and energy renovation.
I am independent of contractors and manufacturers. That means I sell no construction work and no building products, and I take no commission from anyone for recommendations.
Industrial engineer (studying civil engineering) · DGNB Consultant and Auditor · BIM Manager and Coordinator · Sustainabim, Dresden
Existing buildings: for generations, not for a single era.
What owners say.
Who this is for — and who it isn’t.
For you if …
- you own, inherit or are buying a period building.
- a recommendation or a quote is on the table and you can’t judge how much of it is necessary.
- you are thinking about a heat pump and are being told it only works with façade insulation.
- you want to decide for yourself, but not blind.
Not for you if …
- you are planning a new build.
- you are looking for tradespeople rather than a basis for your decision.
- you are looking for someone to take everything off your hands. My office offers design and site supervision as separate commissions.
In the free initial conversation, we will clarify whether your case fits and which step is the right one.
What does an independent engineer do for owners of period buildings?
Thomas Tergan of Sustainabim checks what a private owner’s period building needs before any money is spent: he reads the fabric, classifies planned measures as necessary, advisable, optional or questionable, and checks recommendations and quotes for technical and economic plausibility before contracts are awarded — this is not a legal review of the contract. He sells no construction work and no building products and takes no commission for recommendations. Site visits in Dresden and the surrounding area; the Altbau-Sprechstunde by video from anywhere in Germany.
Before you call.
Do you earn anything from tradespeople or products?
No. I am independent of contractors and manufacturers. That means I sell no construction work and no building products, and I take no commission from anyone for recommendations.
Video course, Altbau-Sprechstunde or guidance – which suits me?
That depends on where you stand. The video courses show you the way, and you walk it on your own. For some situations that is enough. In the Altbau-Sprechstunde you get concrete answers to your questions. In the “Kein Groschengrab” guidance (in German) I work with you on your house and on your documents: I sort them, check them, put them into plain language and prepare your conversations. If nothing is on the table yet, the guidance comes too early. Then a video course or a guide is the better fit. In the free initial conversation I will tell you which step is right for where you stand. The courses and the Altbau-Sprechstunde are in German as well.
Do you only work in Dresden?
We carry out site visits in Dresden and the surrounding area; further afield by arrangement and on the basis of a quote. The Altbau-Sprechstunde, by contrast, takes place by video and can be booked from anywhere in Germany — you send documents in advance and we review them before the conversation. The conversation is held in German.
What does the initial conversation cost?
Nothing. The free initial conversation by video or phone takes 20 minutes and is for orientation. No detailed advice, no review of documents. Result: a recommendation for the next step.
Do you also take on design and site supervision?
Yes, as separate commissions. Each of the eight services can be commissioned on its own. Many projects start with the building survey and then decide afresh whether design and site supervision should follow. Design and site supervision are not part of the “Kein Groschengrab” guidance.
Does a video course replace an energy consultation?
No. The course does not replace energy, legal or tax advice, nor an individual renovation roadmap (iSFP): that is drawn up by a certified expert — module 4 of The Renovation Roadmap shows you how to find the right one.
Before you sign: 20 minutes.
Tell me what lies ahead for you: which house, which documents, which decision. Afterwards you know which next step makes sense for you.
20 minutes, by video or phone. Free of charge, and you commit to nothing.
Not quite there yet? Get the free guide first.
You don’t need to know everything yourself. You just shouldn’t sign blind any more.
Do you develop, buy or hold existing properties as a company? For residential developers, project developers and portfolio owners: engineering office for existing buildings →