Good morning, ladies and gentlemen, and also from my side, a very warm welcome to DIC's full year results conference call. Today, I'm here with Patrick Weiden, CCMO of DIC Asset, Dirk Oehme, our head of accounting, and my colleague from the investor relations team, Max Breuer. As usual, we will give a short presentation of our results and highlights for the full year 2021, followed by a Q&A session. Before we start with our presentation of the 2021 annual results, let me briefly point out that we also launched a public tender offer for the shares of VIB Vermögen AG this morning. Due to legal restrictions applying in certain countries, we are not able to answer any questions on this subject today during today's conference call. However, the information on the tender offer is available on our website, and our IR team can answer your questions later.
Now I come to the highlights. Ladies and gentlemen, we are proud to present another very successful year in DIC's history. First of all, we achieved all of the goals we have planned for 2021, and we were successful in a year which was still impacted by the COVID-19 pandemic. Let me highlight some milestones that we have reached. First, our letting teams performed very strongly and signed a total of around 309,100 sq m on site. Again, a new record. These lettings will further secure long-term cash flows in both business segments. For our own commercial portfolio, we were able to increase our rents like-for-like by 3.5%. On the valuation side, our commercial portfolio saw an increase of 4%, which corresponds to a value uplift of EUR 85.7 million.
These positive results and activities again led to a FFO increase and new record level now for the first time, reaching a triple-digit number with EUR 107 million. Our strategic decision to increase our logistics exposure back in summer 2020 is bearing fruits. We delivered on our plans to increase our logistics investment in both business segments. Until the year-end 2021, we increased our share of logistics investments from 1% to around 8%. We are one of the most active and efficient deal makers in the investment market. The German commercial real estate transaction market achieved record sales of almost EUR 60 billion in the last year. Thanks to a very high transaction volume of EUR 1.9 billion in 2021, we further grew our AUMs to EUR 11.5 billion, an increase of +20% year-over-year.
This has been the third year in a row where we reach a transaction volume in the area of EUR 2 billion. We have bought a wide variety of assets for our commercial portfolio, for our warehousing, and for our Institutional Business. Acquisition focus was on green buildings and logistics assets. Out of the EUR 242 million we notarized for our own balance sheet, roughly one-third stems from green assets. One of the three assets notarized in 2021 in Mettmann near Düsseldorf has already seen the transfer of ownership in the last quarter of 2021. Overall, we reach a green building quota of 11.6% on the basis of an increased commercial portfolio end of last year and expect this figure to increase further with additional acquisitions and transfers.
As mentioned, with a plus of 15%, we reached a new record high for our lettings. What we see in the market is also reflected in our latest letting results. Tenants are still prepared to pay high rents for high quality space in good locations. Since summer 2021, the demand for office space has come back and is now almost at the normal levels observed prior to the outbreak of Corona. We expect that with the economy continuing to grow and uncertainty declining further, we will see a good letting result also for the year 2022. What has changed is the tenants are becoming more quality conscious and are increasingly incorporating ESG criteria and new work models into their list of requirements for office spaces.
Compared to 2020, when we saw the peak of the pandemic, new lettings in 2021 were almost double the size of the previous year. This also led to an increased average rent for new lettings of +9%. For us, this is a clear signal that companies and their teams still need offices. After all, the office is and will remain a space in which employees can work towards their goals and successes in an agile and modern way. We are well positioned to deliver on that. An example you have seen in our latest news. Just a couple of weeks ago, we signed a lease for around 40,000 sq m in office space to Deutsche Bank at beginning of 2022. What's so special about it is Deutsche Bank has requested an office structure fit for tomorrow's new work format.
DIC therefore remodeled floors according to an innovative new work concept. An important driver of our hybrid business model is our capability to warehouse assets on our own balance sheet with the ultimate goal to transfer them to a new vehicle and investors in our Institutional Business. The most prominent example last year was the so-called Uptown Tower in Munich, which we bought in summer 2021. At the end of 2021, we successfully placed 85% of the shares to institutional investors. In total, we notarized a volume of EUR 880 million of warehousing real estate assets in 2021. Two additional assets in Berlin and Düsseldorf were acquired in Q4, with a transfer of ownership still outstanding. Warehousing of properties gives our business activities in a third-party asset management an additional boost.
We can deliver the right product at the right time and act quickly on upcoming opportunities. An important topic of our 2021 agenda has been ESG, and it will be also in the future. We understand ESG as a key element in our daily working processes, and we were able to implement ESG measures in all units of our organization. In 2021, we made strong progress. As part of our last sustainability report, we also unveiled our comprehensive ESG strategy for the next few years. We defined both short and medium term objectives and set ourselves a clear ESG roadmap. One of our main achievements was the implementation of green finance.
Last year, we arranged more than EUR 1 billion in new financing and refinancing deals, including the placement of a EUR 280 million ESG-linked promissory note throughout the year and the issuance of a EUR 400 million green bond. We will use these funds to finance green projects and increase the share of green buildings within our commercial portfolio to approximately 20% of the market value by end of next year. Also, at year-end, we conducted a stakeholder survey to identify several major ESG topics for which we will formulate new targets. We will report regularly on the progress made with these objectives. We will keep our stakeholders well informed also outside of the reporting cycle via our redesigned ESG website. Ladies and gentlemen, all this progress and the continuous development of our business pays off because we act quickly, creatively, and reliably.
It is therefore no coincidence that we continue to improve the DIC business model every year and have done so again in 2021. For the first time, with EUR 107.2 million, we achieved a triple digit FFO result. As usual, we want to enable our shareholders to participate in our strength and success, which is why we are increasing our dividend for the fourth year in a row. We are therefore proposing a dividend of EUR 0.75 per share at the upcoming virtual general shareholders meeting. This includes the usual scrip dividend option. This corresponds to an attractive dividend yield of 4.9% based on the year-end closing price of 2021. On slide eight, you can see the development of our main income streams. Our income streams showed a strong resilience and growth year-over-year.
Driven by our warehousing activities, acquisitions, and letting work, the gross rental income increased by 8% year-on-year, despite the challenges posed by the pandemic and the sales in the current and previous year. For our gross rental income, we slightly exceeded our forecast of EUR 107 million-EUR 108 million with a total of EUR 108.4 million. Our net rental income rose by 11%- EUR 91.2 million. This was attributable to factors including the EUR 2.9 million decrease in COVID-19 related loss allowances on outstanding rental payments. The ongoing expansion of our Institutional Business led to a significant increase of real estate management fees by 27% to EUR 101.2 million.
While asset management, property management, and development fees were stable on previous year's figure at EUR 35.4 million, transaction fees rose considerably to EUR 65.8 million. In addition, we generated a sales profit of EUR 23.8 million and a profit from associates of EUR 6.5 million from our co-investments in the Institutional Business segment. The profit for the period, adjusted for the non-recurring effect from our refinancing for a big part of our commercial portfolio, reached EUR 69.9 million, only slightly below the previous year, mainly due to the lower profit on disposals. Now let's look at the details of the development of the FFO. As mentioned, compared to the previous period, the main income streams, net rental income and real estate management fees, significantly increased.
Our OpEx increased in line with the growth of the platform and the acquisition and integration of RLI Investors. The net interest result, excluding the prepayment penalty in the context of the refinancing at the year-end, increased due to the new financings to fund our growth and due to the green bond placement. The strong growth of our main income pillars over-exceeded the OpEx growth due to integration of RLI and expansion of the IB business and the higher net interest result. In total, the FFO grew to EUR 107.2 million. Including the sales profit, our FFO, too, reached EUR 131.0 million. Let's now look at our valuation and the adjusted NAV, which takes into account both the value of our balance sheet portfolio, as well as the full value of our asset management business.
The successful growth of our integrated real estate platform, including warehousing activities and our strong strategic expansion of the logistics asset class, including the acquisition of RLI Investors at the beginning of 2021, led to an increase in the value of our institutional business by around 35%. This also has mainly driven the increase of the adjusted NAV to exactly 25 EUR per share, a plus of roughly 13%. On the next slide, I want to give you the usual quick update on our financial structure. Our financing activities are far-sighted and increasingly green. As mentioned before, we arranged our first green financings, such as the placement of an ESG-linked promissory note or the issuance of a green bond. By year-end, we also refinanced a larger part of our commercial portfolio.
The lower financing costs lead to a higher FFO contribution of roughly EUR 5 million per year, starting in 2022. All in all, our financing activities led to further reduction of our average cost of debt to a level of 1.8% and an increase of our average maturity for all financial liabilities to 4.4 years at year-end. The refinancing of our maturities 2022 of EUR 260 million is already secured by the sufficient cash at hand of EUR 547 million. The loan-to-value increased by 400 basis points, and this is mainly due to the acquisition activities for the commercial portfolio. Factoring in the full value of the Institutional Business, the adjusted LTV stood at 41.1% compared to 39.2% at the beginning of the year.
Ladies and gentlemen, last but not least, our guidance for 2022. For our commercial portfolio, we plan acquisitions of EUR 200 million-EUR 300 million and the sales volume of around EUR 100 million. In the Institutional Business, we will deploy the committed equity of our investors as planned and focus on raising additional equity. Our acquisition target for the Institutional Business lies between EUR 1.2 billion and EUR 1.6 billion. Roughly EUR 200 million-EUR 400 million planned to be sold. In the commercial portfolio, we expect to generate a gross rental income of roughly EUR 106 million-EUR 109 million. For our asset management business, we plan real estate management fees in a range between EUR 105 million-EUR 115 million.
All in all, we expect to generate an increase of our FFO to a level of EUR 115 million-EUR 119 million. This guidance is based on a standalone planning for DIC and does not include any inorganic growth. Subject to the condition that the planned acquisition of VIB Vermögen AG takes place as part of the announced tender offer, we expect a slightly increased FFO for 2022. We also stick to our midterm target to reach the AUMs of EUR 15 million . Well, that was from our side. Thank you for taking the time to join our conference call today.